bluuebunny/crossref_metadata_2025 huggingface dataset:
On the instantaneous cutting of a columnar vortex

with non-zero axial flow
Authors: MARSHALL J. S. , KRISHNAMOORTHY S.
Published: July 2002

A study of the response of a columnar vortex with non-zero axial
flow

to impulsive

cutting has been performed. The flow evolution is computed based on the

vorticity–velocity formulation of the axisymmetric Euler equation

using a Lagrangian

vorticity collocation method. The vortex response is compared to analytical

predictions obtained using the plug-flow model of Lundgren & Ashurst
(1989).

The plug-flow

model indicates that axial motion on a vortex core with variable core area
behaves

in a manner analogous to one-dimensional gas dynamics in a tube, with

the vortex core

area playing a role analogous to the gas density. The solution

for impulsive cutting of

a vortex obtained from the plug-flow model thus resembles the classic problem
of

impulsive motion of a piston in a tube, with formation of an upstream-propagating

vortex ‘shock’ (over which the core radius changes

discontinuously) and a

downstream-propagating vortex ‘expansion wave’ on

opposite sides of the cutting

surface. Direct computations of the vortex response from the Euler equation
reveal

similar upstream- and downstream-propagating waves following impulsive
cutting for

cases where the initial vortex flow is subcritical. These waves in core
radius are

produced by a series of vortex rings, embedded within the columnar vortex
core,

having azimuthal vorticity of alternating sign. The effect of the compression
and

expansion waves is to bring the axial and radial velocity components to
nearly zero

behind the propagating vortex rings, in a region on both sides of

the cutting surface

with ever-increasing length. The change in vortex core radius and the variation
in

pressure along the cutting surface agree very well with the predictions

of the plug-flow

model for subcritical flow after the compression and expansion waves have
propagated

sufficiently far away. For the case where the ambient vortex flow

is supercritical, no

upstream-propagating wave is possible on the compression side of the vortex,
and the

vortex axial flow is observed to impact on the cutting surface

in a manner similar to

that commonly observed for a non-rotating jet impacting on a wall. The
flow appears

to approach a steady state near the point of impact after a sufficiently

long time. The

vortex response on the expansion side of the cutting surface exhibits a

downstream-propagating vortex expansion wave for both the subcritical

and supercritical

conditions. The results of the vortex response study are used to formulate

and verify predictions for the net normal force exerted by the vortex on
the

cutting surface. An

experimental study of the cutting of a vortex by a thin blade has

also been performed

in order to verify and assess the limitations of the instantaneous

vortex cutting model

for application to actual vortex–body interaction problems.
The effects of a favourable pressure gradient and
of the Reynolds number on an incompressible
axisymmetric turbulent boundary layer. Part 1. The turbulent boundary layer
Authors: FERNHOLZ H. H. , WARNACK D.
Published: July 2002

The effects of a favourable pressure gradient
(K[les ]4×10−6) and of the Reynolds number

(862[les ]Reδ2[les ]5800) on the mean

and fluctuating quantities of four turbulent
boundary layers were studied experimentally and are presented in this paper
and a
companion paper (Part 2). The measurements consist of extensive hot-wire
and skin-friction
data. The former comprise mean and fluctuating velocities, their correlations

and spectra, the latter wall-shear stress measurements obtained by four
different
techniques which allow testing of calibrations in both laminar-like and
turbulent
flows for the first time. The measurements provide complete data sets,
obtained in
an axisymmetric test section, which can serve as test cases as specified
by the 1981
Stanford conference.

Two different types of accelerated boundary layers were investigated
and are
described: in this paper (Part 1) the fully turbulent, accelerated boundary
layer
(sometimes denoted laminarescent) with approximately local equilibrium
between
the production and dissipation of the turbulent energy and with relaxation
to a zero
pressure gradient flow (cases 1 and 3); and in Part 2 the strongly accelerated
boundary
layer with ‘inactive’ turbulence, laminar-like mean flow behaviour
(relaminarized),
and reversion to the turbulent state (cases 2 and 4). In all four cases
the standard
logarithmic law fails but there is no single parametric criterion which
denotes the
beginning or the end of this breakdown. However, it can be demonstrated
that the
departure of the mean-velocity profile is accompanied by characteristic
changes of
turbulent quantities, such as the maxima of the Reynolds stresses or the
fluctuating
value of the skin friction.

The boundary layers described here are maintained in the laminarescent
state just
up to the beginning of relaminarization and then relaxed to the turbulent
state in a
zero pressure gradient. The relaxation of the turbulence structure occurs
much faster
than in an adverse pressure gradient. In the accelerating boundary layer
absolute
values of the Reynolds stresses remain more or less constant in the outer
region of
the boundary layer in accordance with the results of Blackwelder &
Kovasznay (1972),
and rise both in the vincinity of the wall in conjunction with the rising
wall shear
stress and in the centre region of the boundary layer with the increase
of production.
Marangoni convection in binary mixtures with Soret effect
Authors: BERGEON A. , HENRY D. , BENHADID H. , TUCKERMAN L. S.
Published: July 2002

Marangoni convection in a differentially heated binary mixture
is studied numerically
by continuation. The fluid is subject to the Soret effect and is contained
in a two-dimensional
small-aspect-ratio rectangular cavity with one undeformable free surface.

Either or both of the temperature and concentration gradients may be destabilizing;

all three possibilities are considered. A spectral-element time-stepping
code is adapted
to calculate bifurcation points and solution branches via Newton's
method. Linear
thresholds are compared to those obtained for a pure fluid. It is found
that for large
enough Soret coefficient, convection is initiated predominantly by solutal
effects and
leads to a single large roll. Computed bifurcation diagrams show a marked
transition
from a weakly convective Soret regime to a strongly convective Marangoni
regime
when the threshold for pure fluid thermal convection is passed. The presence
of many
secondary bifurcations means that the mode of convection at the onset of
instability
is often observed only over a small range of Marangoni number. In particular,

two-roll states with up-flow at the centre succeed one-roll states via
a well-defined
sequence of bifurcations. When convection is oscillatory at onset, the
limit cycle is
quickly destroyed by a global (infinite-period) bifurcation leading to
subcritical steady
convection.
Flow behind castellated blunt-trailing-edge
aerofoils at supersonic speeds
Authors: MAGI E. C. , GAI S. L.
Published: July 2002

A study of the near-wake flow of castellated blunt-trailing-edge
aerofoils at a Mach
number of 2 was conducted to understand the nature of the flow and the
mechanisms
of base pressure recovery. The investigation has shown that strong gradients
exist in
the spanwise direction and that the formation of the wake recompression
shock occurs
further away from the wake axis. Also, the wake neck is broader and diffused.
Detailed
quantitative data involving pressure measurements, schlieren and holographic

interferometry, and laser transit velocimetry, are presented. A theoretical
model to
predict the mean base pressure on a castellated base is also proposed.
Comparison with
experimental data shows that the model provides a qualitative description
of the flow
behind a castellated base at supersonic speeds.
Motion of a sphere near planar confining
boundaries in a Brinkman medium
Authors: FENG J. , GANATOS P. , WEINBAUM S.
Published: July 2002

A general numerical method using the boundary integral equation
technique of
Pozrikidis (1994) for Stokes flow in an axisymmetric domain is used to
obtain the first
solutions to the Brinkman equation for the motion of a particle in the
presence of
planar confining boundaries. The method is first applied to study the perpendicular

and parallel motion of a sphere in a fibre-filled medium bounded by either
a solid
wall or a planar free surface which remains undeformed. By accurately evaluating

the singular integrals arising from the discretization of the resulting
integral equation,
one can efficiently and accurately treat flow problems with high α
defined by
rs/K1/2p

in which rs is the radius of the sphere and

Kp is the Darcy permeability. Convergence

and accuracy of the new technique are tested by comparing results for the
drag with
the solutions of Kim & Russell (1985a) for the motion of two
spheres perpendicular
to their line of centres in a Brinkman medium. Numerical results for the
drag and
torque exerted on the particle moving either perpendicular or parallel
to a confining
planar boundary are presented for ε[ges ]0.1, in which
εrs is the gap between the
particle and the boundary. When the gap width is much smaller
than rs, a local
analysis using stretched variables for motion of a sphere indicates that
the leading
singular term for both drag and torque is independent of α
provided that α = O(1).
These results are of interest in modelling the penetration of the endothelial
surface
glycocalyx by microvilli on rolling neutrophils and the motion of colloidal
gold and
latex particles when they are attached to membrane receptors and observed
in nanovid
(video enhanced) microscopy. The method is then applied to investigate
the motion
of a sphere translating in a channel. The drag and torque exerted on the
sphere are
obtained for various values of α, the channel height
H and particle position b. These
numerical results are used to describe the diffusion of a spherical solute
molecule in a
parallel walled channel filled with a periodic array of cylindrical fibres
and to assess
the accuracy of a simple multiplicative formula proposed in Weinbaum et
al. (1992)
for diffusion of a solute in the interendothelial cleft.
On the nonlinear stability of the oscillatory
viscous flow of an incompressible fluid in a
curved pipe
Authors: SHORTIS TRUDI A. , HALL PHILIP
Published: July 2002

The stability of the flow of an incompressible, viscous fluid through
a pipe of circular
cross-section, curved about a central axis is investigated in a weakly
nonlinear regime.
A sinusoidal pressure gradient with zero mean is imposed, acting along
the pipe.
A WKBJ perturbation solution is constructed, taking into account the need
for an
inner solution in the vicinity of the outer bend, which is obtained by
identifying the
saddle point of the Taylor number in the complex plane of the cross-sectional
angle
coordinate. The equation governing the nonlinear evolution of the leading-order
vortex
amplitude is thus determined. The stability analysis of this flow to axially
periodic
disturbances leads to a partial differential system dependent on three
variables, and
since the differential operators in this system are periodic in time, Floquet
theory may
be applied to reduce it to a coupled infinite system of ordinary differential
equations,
together with homogeneous uncoupled boundary conditions. The eigenvalues
of this
system are calculated numerically to predict a critical Taylor number consistent
with
the analysis of Papageorgiou (1987). A discussion of how nonlinear effects
alter the
linear stability analysis is also given. It is found that solutions to
the leading-order
vortex amplitude equation bifurcate subcritically from the eigenvalues
of the linear
problem.
Numerical simulation of converging nonlinear wavefronts
Authors: PRASAD PHOOLAN , SANGEETA K.
Published: July 2002

The propagation of a two-dimensional weakly nonlinear wavefront into a polytropic

gas in a uniform state and at rest has been studied. Successive positions of the

wavefront and the distribution of amplitude on it are obtained by solving a system of

conservation forms of the equations of weakly nonlinear ray theory (WNLRT) using

a TVB scheme based on the Lax–Friedrichs flux. The predictions of the WNLRT

are found to be qualitatively quite different from the predictions of the linear theory.

The linear wavefronts leading to the formation of caustics are replaced by nonlinear

wavefronts with kinks. By varying the initial shape of the wavefront and the amplitude

distribution on it, the formation and separation of kinks on the wavefront has been

studied.
On Rayleigh's computation of the ‘end

correction’, with application to the compression

wave generated by a train entering a tunnel
Authors: HOWE M. S.
Published: July 2002

Rayleigh's (1926, Appendix A) method for the approximate calculation of potential

flow from the open end of a semi-infinite flanged cylinder is applied to obtain

analytical representations of Green's function describing the generation of sound

waves within a flanged cylinder by sources located in the neighbourhood of the

open end. Detailed results are given for the circular cylinder considered by Rayleigh

and extension made to a flanged cylinder of rectangular cross-section. The validity of

various approximations is assessed by comparison with the exact solution available (by

the method of conformal transformation) for potential flow from a two-dimensional,

flanged duct. The results are used to compare the profiles and the pressure gradients

of compression waves generated when a high-speed train enters tunnels of circular

and rectangular cross-sections.
Structure and stability of non-symmetric Burgers vortices
Authors: PROCHAZKA AURELIUS , PULLIN D. I.
Published: July 2002

We investigate, numerically and analytically, the structure and
stability of steady
and quasi-steady solutions of the Navier–Stokes equations corresponding
to stretched
vortices embedded in a uniform non-symmetric straining field,
(αx, βy, γz), α+β+γ=0,

one principal axis of extensional strain of which is aligned with the vorticity.
These are
known as non-symmetric Burgers vortices (Robinson & Saffman 1984).
We consider
vortex Reynolds numbers R=Γ/(2πv) where
Γ is the
vortex circulation and v the kinematic viscosity, in the range

R=1−104, and a broad range of strain ratios
λ=(β−α)/(β+α) including λ>1,

and in some cases λ[Gt ]1. A pseudo-spectral method is used to obtain numerical solutions corresponding to steady and quasi-steady vortex states over our whole (R, λ) parameter space including λ where arguments
proposed by Moffatt, Kida & Ohkitani (1994) demonstrate the non-existence
of
strictly steady solutions. When λ[Gt ]1, R[Gt ]1 and
ε≡λ/R[Lt ]1, we find an accurate
asymptotic form for the vorticity in a region
1<r/(2v/γ)1/2[les ]ε1/2,

giving very good agreement with our numerical solutions. This suggests
the existence
of an extended region where the exponentially small vorticity is confined

to a nearly cat's-eye-shaped
region of the almost two-dimensional flow, and takes a constant value nearly
equal
to Γγ/(4πv)exp[−1/(2eε)]

on bounding streamlines. This allows an estimate of the
leakage rate of circulation to infinity as
∂Γ/∂t
=(0.48475/4π)γε−1Γ
exp (−1/2eε) with corresponding exponentially slow
decay of the
vortex when λ>1. An iterative technique based on the power
method is used to estimate the largest eigenvalues
for the non-symmetric case λ>0. Stability is found for 0[les ]λ[les ]1,

and a neutrally convective mode of instability is found and analysed for
λ>1.
Our general conclusion is that the generalized non-symmetric Burgers vortex

is unconditionally stable to two-dimensional disturbances for all
R, 0[les ]λ[les ]1, and that when λ>1, the vortex

will decay only through exponentially slow leakage of vorticity, indicating
extreme
robustness in this case.
On the evolution of non-axisymmetric viscous
fibres with surface tension, inertia and gravity
Authors: CUMMINGS L. J. , HOWELL P. D.
Published: July 2002

We consider the free boundary problem for the evolution of a nearly straight slender
fibre of viscous fluid. The motion is driven by prescribing the velocity of the ends of
the fibre, and the free surface evolves under the action of surface tension, inertia and
gravity. The three-dimensional Navier–Stokes equations and free-surface boundary
conditions are analysed asymptotically, using the fact that the inverse aspect ratio,
defined to be the ratio between a typical fibre radius and the initial fibre length, is
small. This first part of the paper follows earlier work on the stretching of a slender
viscous fibre with negligible surface tension effects. The inclusion of surface tension
seriously complicates the problem for the evolution of the shape of the cross-section.
We adapt ideas applied previously to two-dimensional Stokes flow to show that the
shape of the cross-section can be described by means of a conformal map which
depends on time and distance along the fibre axis. We give some examples of suitable
relevant conformal maps and present numerical solutions of the resulting equations.
We also use analytic methods to examine the coupling between stretching and the
evolution of the cross-section shape.
Competition between distributed and localized buoyancy fluxes in
a confined volume
Authors: WELLS M. G. , GRIFFITHS R. W. , TURNER J. S.
Published: July 2002

We investigate the convection and density stratification that form when buoyancy
fluxes are simultaneously applied to a finite volume in both a turbulent buoyant
plume from a small source and as a uniform heat flux from a horizontal boundary.
The turbulent plume tends to produce a stable density stratification, whereas the
distributed flux from a boundary tends to force vigorous overturning and vertical
mixing. Experiments show that steady, partially mixed and partially stratified states
can exist when the plume buoyancy flux is greater than the distributed flux.

When the two fluxes originate from the same boundary, the steady state involves
a balance between the rate at which the mixed layer deepens due to encroachment
and vertical advection of the stratified water far from the plume due to the plume
volume flux acquired by entrainment. There is a monotonic relationship between
the normalized mixed layer depth and flux ratio R (boundary flux/plume flux) for
0<R<1, and the whole tank overturns for R>1. The stable density gradient in the
stratified region is primarily due to the buoyancy from the plume but is strengthened
by a stabilizing temperature gradient resulting from entrainment of heat into the
plume from the mixed layer. This result may be relevant to the upper oceans of high
latitude where there is commonly a destabilizing heat flux from the sea surface as
well as more localized and intense deep convection from the surface.

For the case of fluxes from a plume on one boundary and a uniform heat flux from
the opposite boundary the shape of the density profile is that given by the Baines &
Turner (1969) ‘filling-box’ mechanism, with the gradient reduced by a factor
(1 + R) due to the heating. Thus, when R<−1 there is no stratified region and
the whole water column overturns. When 0>R>−1, the constant depth of the
convecting layer is determined by a balance between buoyancy and turbulent kinetic energy in
the outflow layer from the plume.
Turbulent dispersion in a non-homogeneous field
Authors: ILIOPOULOS ILIAS , HANRATTY THOMAS J.
Published: July 2002

Dispersion of fluid particles in non-homogeneous turbulence was studied for fully
developed flow in a channel. A point source at a distance of 40 wall units from the
wall is considered. Data obtained by carrying out experiments in a direct numerical
simulation (DNS) are used to test a stochastic model which utilized a modified
Langevin equation. All of the parameters, with the exception of the time scales, are
obtained from Eulerian statistics. Good agreement is obtained by making simple
assumptions about the spatial variation of the time scales.
Surface shear viscosity of Gibbs and Langmuir monolayers
Authors: BARENTIN CATHERINE , YBERT CHRISTOPHE , DI MEGLIO JEAN-MARC , JOANNY JEAN-FRANÇOIS
Published: July 2002

In this paper, we present a new two-dimensional viscometer, and the hydrodynamic
calculations used to obtain the surface viscosities from the measurements. In order to
interpret the experiments, performed with solutions of sodium dodecyl sulfate (SDS)
and also with monolayers of insoluble surfactants, we develop various hydrodynamic
models of soluble Gibbs monolayers and of incompressible Langmuir monolayers,
that describe well the experimental results. In the case of SDS solutions, the calculations
allow the determination of the surface shear viscosity, and its value is in good
agreement with previous studies.
Experimental study of the stability of deep-water
wave trains including wind effects
Authors: WASEDA TAKUJI , TULIN MARSHALL P.
Published: July 2002

An experimental investigation on the initial instability of nonlinear deep-water wave
trains including wind effects is reported. The experiment was conducted at the Ocean
Engineering Laboratory wind-wave facility (50 m long, 4.2 m wide, 2.1 m deep), with
a fully computer-controlled mechanical wave generator to explore the parameter
space: steepness; sideband frequency; wind speed. The estimated growth rates of
the Benjamin–Feir instability from seeded wind-free experiments agreed well with
the theoretical prediction derived from Krasitskii's four-wave reduced equation as
computed here. Wind was added to the same wave system; the growth rates of the
sidebands were reduced for weak, and enhanced for strong wind forcing. Experiments
with naturally selected sidebands, i.e. unseeded, were conducted as well; measurements
showed that wind did not inhibit the growth of sidebands in the case of either two-dimensional or three-dimensional instabilities. A comparison of the results with earlier
work suggests that there are two independent effects of wind: first, the alteration of
the inviscid growth for a given modulational frequency as shown by comparison with
the seeded experiments without wind; second, a change in the natural modulational
frequency appearing in the presence of wind which is a function of the wave age,
as observed in unseeded experiments. Both effects combined will determine whether
the modulational instability is enhanced or suppressed; comparison of experimental
results with theoretical predictions suggests that the effect of wind on the natural
selection of the modulational frequency is the dominant effect. It was shown that
for moderate to old waves, the net effect of wind on the modulational instability is
small. For all the experiments except a few unseeded cases with weak breakers, the
modulation was small and no breaking was observed within the tank.
Dynamics of a low Reynolds number turbulent boundary layer
Authors: CHACIN JUAN M. , CANTWELL BRIAN J.
Published: July 2002

The generation of Reynolds stress, turbulent kinetic energy and dissipation in the
turbulent boundary layer simulation of Spalart (1988) is studied using the invariants
of the velocity gradient tensor. This technique enables the study of the whole range of
scales in the flow using a single unified approach. In addition, it also provides a rational
basis for relating the flow structure in physical space to an appropriate statistical
measure in the space of invariants. The general characteristics of the turbulent motion
are analysed using a combination of computer-based visualization of flow variables
together with joint probability distributions of the invariants. The quantities studied
are of direct interest in the development of turbulence models. The cubic discriminant
of the velocity gradient tensor provides a useful marker for distinguishing regions
of active and passive turbulence. It is found that the strongest Reynolds-stress and
turbulent-kinetic-energy generating events occur where the discriminant has a rapid
change of sign. Finally, the time evolution of the invariants is studied by computing
along particle paths in a Lagrangian frame of reference. It is found that the invariants
tend to evolve toward two distinct asymptotes in the plane of invariants. Several
simplified models for the evolution of the velocity gradient tensor are described.
These models compare well with several of the important features observed in the
Lagrangian computation. The picture of the turbulent boundary layer which emerges
is consistent with the ideas of Townsend (1956) and with the physical picture of
turbulent structure set forth by Theodorsen (1955).
Judicial Independence: The Politics of the Supreme Court in Mexico
Authors: DOMINGO PILAR
Published: July 2002

This article examines the role of the Supreme Court in the development
of the Mexican political system. The judiciary provided an important source of
regime legitimation, as it allowed for the consolidation of a state of legality and
a claim to constitutional rule of law, at least in discourse. However, the judiciary
was in effect politically subordinated to the logic of dominant party rule through
both specific constitutional reforms since 1917 that weakened the possibility of
judicial independence and a politics of institutional and political co-optation. The
constitutional reform of 1994 has significantly altered the nature of the
relationship between the executive and the Supreme Court.
A Political Analysis of Legal Pluralism in Bolivia and Colombia
Authors: VAN COTT DONNA LEE
Published: July 2002

In this article the author compares recent efforts in Bolivia and
Colombia to implement constitutionally mandated regimes of legal pluralism, and
identifies the most important factors affecting the practical realisation of legal
pluralism: the capacity of the political system, the legal tradition and society to
tolerate normative diversity; the geographic isolation and cultural alienation of
indigenous communities; the degree of internal division within indigenous
communities and movements regarding legal pluralism in general, and in specific
cases, that have arisen, and the availability of effective legal mechanisms to
indigenous communities seeking to protect this right.
The Prague School and North American functionalist approaches to syntax
Authors: NEWMEYER FREDERICK J.
Published: July 2002

Modern functionalist approaches to syntax were pioneered in the 1920s by the
scholars associated with the Linguistic Circle of Prague and Prague-based
functionalism is a dynamic force today. Nevertheless, citations of this work by North
American functionalists are few and far between. This paper sets out to explain that
state of affairs. It pinpoints the profound theoretical differences between mainstream
North American and Czech approaches that have led to partisans of the former losing
interest in the latter. The paper argues that, on the other hand, Praguian functional
syntax has a great deal in common with more ‘formal’ functionalist approaches and
with much work in formal semantics. Not surprisingly, then, recent years have seen
increasing productive collaboration between North American and Western European
practitioners of these approaches and members of the Prague School.
Viscous interface instability supporting free-surface currents in a hydromagnetic rotating fluid column
Authors: EL-DIB YUSRY O.
Published: July 2002

The stabilization of a viscous interface stressed by an oscillating
magnetic field is investigated. Account is taken of the influence of free-surface
currents on the effective solidly rotating fluid column. Only azimuthal modes
are considered in the linear perturbation. The dispersion relation with or
without free-surface currents is obtained in the form of a linear Mathieu
equation with complex coefficients. It is found that there is a nonlinear relation
between the surface current density and both the stratified viscosity and the
stratified azimuthal magnetic field. The surface currents disappear on the
interface of the fluid column when the stratified magnetic field has the value of
unity. At this value, a coupled parametric resonance occurs in the absence of
angular velocity. The magnetic field plays a stabilizing role. This role increases
with increasing surface currents. The angular velocity plays a destabilizing role,
while the field frequency plays a stabilizing role and acts against the angular
velocity. The stratified viscosity plays a damping role in the presence of the
surface current density, while, in the absence of a surface current, it plays two
opposite roles corresponding to the presence or absence of the field frequency.
A set of graphs are used to illustrate the relation between the presence of free-surface
currents and both the viscosity and the azimuthal magnetic field.
Anisotropy in Hall MHD turbulence due to a
mean magnetic field
Authors: GHOSH S. , GOLDSTEIN M. L.
Published: July 2002

The development of anisotropies in an initially isotropic spectrum
is studied
numerically for compressible magnetohydrodynamic (MHD) turbulence in the
presence of the Hall term. Building on a previous study where it was shown
that
spectral cascades in the Hall MHD system differ from the standard MHD case,
particularly at high cross-helicities, we use an isotropic high cross-helicity
initial state to study anisotropies of the Hall MHD system for a variety
of mean
magnetic field strengths and sonic Mach numbers. Strong anisotropies, which
maximize at the ion-inertial length scale, appear for several plasma states
and
are categorized according to their plasma beta β: high-β Hall
MHD simulations
(β>1) show strong anisotropies relative to the standard MHD case,
intermediate-β Hall MHD simulations (β≈1) show smaller anisotropy
differences relative to the standard MHD case, and low-β Hall MHD
simulations
(β<1) again show strong anisotropies relative to the standard model.
It is
suggested that these anisotropy enhancements are due to nonlinear cascade
suppression of propagating Alfvén waves in the field-aligned direction.
This is different from the dynamics in the highly oblique directions, where
non-propagating density and magnetic-energy anticorrelations appear.
Dedication
Authors: Baus Marc
Published: July 2002

This issue of the Journal of Plasma Physics is dedicated
to
Radu Balescu on the occasion of his 65th birthday.

Of the more than 170 articles published worldwide by Professor Balescu
to
date, more than 25 have been published in this journal. Readers of the
Journal
of Plasma Physics will thus be well acquainted with his contributions
to the
study of the interplay between plasma turbulence and the theory of transport

phenomena in magnetically confined plasmas. A vast community of students,

teachers and researchers will also have read or consulted the many monographs,

five to date, written by Balescu and world-famous for their clarity. In
his first
monograph, Statistical Mechanics of Charged Particles (Interscience,
New York),
published in 1963, the whole of plasma physics, including the transport

equation to which his name will remain attached, was put into the broader

context of statistical physics. The monograph Equilibrium and Non-Equilibrium

Statistical Mechanics (Wiley-Interscience, New York) followed in 1975,
and still
inspires many teachers today.
Articulatory and acoustic effects of lip-plate speech in Chai and its implications for phonological theory
Authors: Yigezu Moges
Published: July 2002

The custom of lip-plate insertion, as practiced by the Chai people, has an effect on the speech of women since it alters articulators needed for speech production: the lower lip and the lower incisors. Due to the effect of this practice, women cannot produce bilabial and dental consonants in their own language. Vowels are also affected, but the presence of the lip-plate does not affect the tonal system. This study further examines ways in which the lower lip and lower incisor mutilations are compensated for, and the acoustic effects involved in the ‘lip-plate speech’ as well as its implications for phonological theory.
Age and growth of the echinoid Sphaerechinus granularis from the Algerian coast
Authors: Soualili Dina Lila , Guillou Monique , Semroud Rachid
Published: July 2002

The growth bands in the plates of the echinoid Spharechinus granularis settled on the Algerian coast were analysed. Two distinct groups of sea urchins were identified with different growth patterns related to the period of recruitment, i.e. spring or autumn. The growth rate of the autumn cohort was higher over the year following the first winter after settlement. From the second winter there was little growth difference between the two cohorts. Compared to populations from Atlantic sites, the Algerian population has a lower growth rate and reduced longevity.
The Human Rights Issue in China, 1929-1931
Authors: FUNG EDMUND S K
Published: July 2002

In recent years the issue of human rights in China has been in the international limelight, especially since the Beijing Massacre of 4 June 1989. It is, however, not a new issue in the history of modern and contemporary China. Earlier in the 1970s and 1980s, a movement for Chinese democracy and human rights was launched by dissidents, though with little success. Nor is it widely known that during the first years of the Nationalist rule there was a short-lived Human Rights Group (HRG) made up of a small number of Western-educated intellectuals.
Muslims' Perception of Judaism and Christianity in Medieval India
Authors: Ali M. Athar
Published: July 2002

As is well known, Islam arose in Arabia, which, alongside the pagan Communities, had a large number of tribes and groups which professed Judaism and Christianity. So far as we know, the relations between the Jews and Christians and their Arab neighbours in pre-Islamic times were cordial, or were not at any rate adversely affected by differences of faith. In its self-view Islam represented both a continuation and a supersession of the two earlier Semitic faiths. The Jewish Gospel as well as the New Testament had originally represented divine messages, and so those who follow them were ‘People of the Book’, to be distinguished from the ‘Infidels’. But the Gospel texts, the Quran itself had claimed, had suffered from unauthorized deletions and insertions; and this claim, of course, created a fundamental point of disagreement between the Muslims, on the one hand, and the Jews and Christians on the other. Nonetheless, early Muslims seemed fairly well familiar with both the earlier Semitic religions.
THE SHIPWRECKS OF ODYSSEUS AND PAUL
Authors: MACDONALD DENNIS R.
Published: July 2002

Acts 27–28 frequently points to the shipwrecks of Odysseus in Odyssey Books 5 and 12, the second of which the hero narrates in the first person. The shipwrecks of Odysseus and Paul share nautical images and vocabulary, the appearance of a goddess or angel assuring safety, the riding of planks, the arrival of the hero on an island among hospitable strangers, the mistaking of the hero as a god, and the sending of him on his way. Luke's intention in relating Paul's shipwreck to those of Odysseus was to exalt Paul and his God by comparison.
The in vitro development of the pentastomid Porocephalus
crotali from the infective instar to the adult stage
Authors: BUCKLE A. C. , RILEY J. , HILL G. F.
Published: July 2002

The in vitro development of the pentastomid Porocephalus
crotali from the infective, seventh (VII) instar, dissected from
the tissues of rat intermediate hosts, to the adult male (X) and female
(XI)
instars, normally resident in the lung of
rattlesnake definitive hosts, is described. The culture medium comprised
washed human blood cells, resuspended in bovine
serum (50[ratio ]50, v/v), with 20% minimum essential medium and
antibiotics. Two batches of approximately 100 pentastomids, maintained
at a
density of 2 worms/ml, were cultured in 500 ml bottles in an atmosphere
of 5% CO2 in air at
28°C. Culture bottles were rotated slowly on a Rollacell system and the
medium
was replenished every 2–3 days. Growth
was monitored at various intervals by weighing worms, measuring cast
cuticles with attached moulted hooks recovered
from the medium, and by dissecting worms for measurements of various organ
systems. Three moults separated the
infective and adult male instar, whereas 4 moults were necessary in the
case
of females. In both cultures natural mortality
was about 10% over a 160-day period, by which time 33–51% of
females and 62–70% of males had reached the
terminal instar. Some males attained full sexual maturity with seminal
vesicles loaded with viable sperm: such males were
indistinguishable from males recovered from naturally infected rattlesnakes.
However, females never achieved full size,
even after 200 days, and although copulation did not occur in vitro,
some females became patent.
Inhibition of the development of Eimeria tenella in
cultured bovine kidney cells by a soluble factor produced
by peripheral blood lymphocytes from immune chickens
Authors: BUMSTEAD J. M. , TOPHAM S. J. , TOMLEY F. M.
Published: July 2002

The intracellular development of Eimeria tenella sporozoites

in in vitro cultured Madin–Darby Bovine Kidney (MDBK)
cells was inhibited when parasite-infected MDBK cells were incubated
with peripheral blood lymphocytes (PBL) from
infected chickens. The inhibition mediated by PBL was quantified by
[3H]uracil uptake and increased during the course

of a series of oral infections of chickens with E. tenella.
This was mirrored by the development of immunity in these birds,
as assessed by counting the oocyst output following each re-infection.

Similar levels of inhibition were observed using
PBL from 3 inbred lines of chickens which differ in their relative
susceptibility to infection with E. tenella, indicating that
the genetic background of the host does not influence the production of

this inhibitory activity. The inhibition could be
transferred to freshly infected MDBK cells using supernatants prepared

from parasite-infected monolayers incubated for
48 h with PBL from immune chickens. However, there was no inhibition using

either supernatants from infected MDBK
cells incubated with PBL from uninfected chickens, or supernatants from

uninfected MDBK cells incubated with PBL
from immune chickens. Experiments using Transwell plates showed that
direct contact of PBL from immune birds with
infected MDBK monolayers was not required to produce supernatants with

inhibitory activity. Thus production of soluble
inhibitory factor(s) by PBL from immune chickens can be specifically
induced by soluble antigens present in the culture
media of parasite-infected MDBK cells. These factors inhibit the
intracellular development of sporozoites in in vitro culture.
A Useful Time Machine
Authors: Goddu G. C.
Published: July 2002

Robert Casati and Achille C. Varzi, argue that time machines would be useless or have no practical applications on the grounds that travelling to the past would involve doing what has already been done. I argue that the sense in which travelling to the past involves doing what has already been done fails to support the claim that time machines would have no practical applications.
Tribute to Renford Bambrough (1926–1999)
Authors: Brearley Michael
Published: July 2002

As we reported in the April issue of Philosophy, Renford Bambrough, the editor of Philosophy from 1972 to 1994, died on January 17th, 1999. During the memorial service at St John's College, Cambridge, on the 24th of April, 1999, the following extract from Renford Bambrough's Sermon at the Commemoration of Benefactors, 1968, was read:

I know that you know all this, or you would not be here. But I also know, from some things that some of you and some others have said and written, that some of you need to be reminded of what you know.
Hypochondriacal concerns in a community population
Authors: LOOPER KARL J. , KIRMAYER LAURENCE J.
Published: July 2002

Background. Hypochondriasis is recognized as an important disorder in clinical populations, associated with increased health care utilization, disability and psychiatric co-morbidity. Few studies have investigated hypochondriasis in the community. We report on the broader concept of illness worry in a community population.

Methods. Five hundred and seventy-six subjects from an ethnically diverse urban setting were surveyed. Information was gathered on sociodemographic variables, medical and psychiatric status, health care utilization and disability. Bivariate and multivariate regression analyses were used to compare groups with illness worry (with and without the medical condition) to those without illness worry.

Results. Only one subject of 533 (0·2 %) met criteria for hypochondriasis and seven (1·3 %) fulfilled abridged criteria. However, 33 (6 %) of the sample had illness worry. Of these, 17 had the illness about which they worried. Compared with controls, both illness worry groups had elevated levels of medical illness, psychiatric symptoms, help-seeking, health care use and disability. In multiple regression analyses, illness worry was an independent predictor of somatic symptoms, help-seeking, and disability, when sociodemographic and medical variables were controlled.

Conclusions. Hypochondriasis appears to be a rare disorder in the community while illness worry is relatively common. Illness worry was present in equal numbers of subjects with the illness of concern, as those without. Illness worry was an independent factor contributing to increased levels of distress, health care utilization, and disability, even when medical status was controlled, suggesting that it is an important issue for further research.
A general population comparison of the Composite International Diagnostic Interview (CIDI) and the Schedules for Clinical Assessment in Neuropsychiatry (SCAN)
Authors: BRUGHA T. S. , JENKINS R. , TAUB N. , MELTZER H. , BEBBINGTON P. E.
Published: July 2002

Background. In psychiatric surveys of the general population, there has been considerable discrepancy between diagnoses obtained by fully structured interviews and those established by systematic semi-structured clinical evaluation. The Composite International Diagnostic Interview (CIDI) is an example of the first type of interview widely used in general population surveys. We compared its performance in diagnosing current depressive and anxiety disorders with the Schedules for Clinical Assessment in Neuropsychiatry (SCAN), a semi-structured diagnostic interview administered by clinically trained interviewers.

Methods. Household addresses in Leicestershire, UK, were randomly sampled and 860 adults were screened with the Revised Clinical Interview Schedule. Adults with too few symptoms to fulfil diagnostic criteria for study disorders were excluded to increase the proportion re-interviewed who met such criteria. Repeat diagnostic interviews with the CIDI and SCAN, ordered randomly, were sought from eligible screen positive respondents. Recalibrated CIDI prevalence estimates were derived from the SCAN classification using Bayesian statistics.

Results. Concordance ranged between ‘poor’ and ‘fair’ across almost all types of study disorders, and for co-morbidity. Concordance was somewhat better for severity of depression and when lower diagnostic thresholds were used for depression. Interview order effects were suggested with lower concordance when CIDI followed SCAN. Recalibration reduced the prevalence of depressive or anxiety disorder from 9·0 to 6·2%.

Conclusions. Community psychiatric surveys using structured diagnostic interview data must be interpreted cautiously. They should include an element of clinical re-appraisal so findings can be adjusted for estimation differences between fully structured and clinical assessments.
A factor model of the functional psychoses and the
relationship of factors to clinical variables and brain
morphology
Authors: McINTOSH A. M. , FORRESTER A. , LAWRIE S. M. , BYRNE M. , HARPER A. , KESTELMAN J. N. , BEST J. J. K. , MILLER P. , JOHNSTONE E. C. , OWENS D. G. C.
Published: July 2002

Background. Despite more than 100 years of study, there remains no definitive diagnostic
validation of the functional psychoses. Factor analysis suggests the presence of three or more
psychopathological syndromes in functional psychoses as a whole. The relationship between these
factors and cerebral anatomy has been investigated in schizophrenia only. This study aimed to
address the relationship of symptom factors to clinically important variables and cerebral anatomy
in a sample of psychotic patients with a spread of diagnoses.

Methods. In a sample of patients with functional psychoses, symptom data was obtained on four
consecutive admissions using the OPCRIT symptom checklist. OPCRIT data was used to generate
operational diagnoses in accordance with pre-set criteria and a principle components analysis was
performed on symptom data. Factor loadings were compared between each admission to examine
factor stability over time. Factor scores at first admission were also correlated with clinical variables
obtained from patients' case notes. From the sample of 204 patients, 64 subjects were recruited and
underwent an MRI scan of the brain. Regional anatomical volumes were compared with diagnosis
and factor loadings at first admission.

Results. A principal components analysis gave a four-factor solution of ‘manic’, ‘depressive’,
‘disorganization’ and ‘reality distortion’ factors at each admission. Factors showed a high degree
of stability over the four admissions studied. The factors were significantly associated with several
clinical variables. Three of the four factors were associated with a specific pattern of cerebral
anatomy.

Conclusions. This study suggests that factors may correspond to relatively specific disease processes
underlying functional psychotic illness. We propose that the use of symptom factors may facilitate
the investigation of the underlying mechanisms of psychotic illness.
Quantitative proton magnetic resonance spectroscopy
of the bilateral frontal lobes in patients with bipolar
disorder
Authors: HAMAKAWA H. , KATO T. , SHIOIRI T. , INUBUSHI T. , KATO N.
Published: July 2002

Background. Using 31P and 1H magnetic resonance spectroscopy (MRS) we previously reported that
phosphocreatine was decreased in the left frontal lobe and choline-containing compounds were
increased in the basal ganglia in the depressive state in patients with bipolar disorder. We applied
quantitative 1H-MRS for further characterization of biochemical alteration in the frontal lobes of
bipolar patients.

Methods. Twenty-three bipolar patients and 20 normal controls were examined by
1H-MRS with a 1.5T MR system. All patients were examined in the
euthymic state, and eight patients were also
examined in the depressive state. Volumes of interest of 2·5×2·5×2·5 cm were selected in the left
and right frontal lobes. Absolute concentrations of N-acetyl-l-aspartate, creatine plus
phosphocreatine, and choline-containing compounds were calculated from each metabolite peak.

Results. Creatine concentration in the left frontal lobe in bipolar patients in the depressive state was
significantly lower than that in the euthymic state. Creatine concentration in the right frontal lobe
in the male patients was significantly higher than that in the female patients and a similar trend was
also found in the control subjects.

Conclusions. We found a state-dependent change of creatine metabolism in the left frontal lobe of
bipolar patients. The present results are compatible with our previous report of decreased
phosphocreatine measured by 31P-MRS in the left frontal lobe in bipolar disorder. We also found
an effect of gender on the creatine concentration. There may be a gender difference in creatine
transport function into the brain.