bluuebunny/crossref_metadata_2025 huggingface dataset:
Compressibility effects in a turbulent annular mixing layer. Part 1. Turbulence and growth rate
Authors: FREUND JONATHAN B. , LELE SANJIVA K. , MOIN PARVIZ
Published: July 2002

This work uses direct numerical simulations of time evolving annular mixing layers,
which correspond to the early development of round jets, to study compressibility
effects on turbulence in free shear flows. Nine cases were considered with convective
Mach numbers ranging from Mc = 0.1 to 1.8 and turbulence Mach numbers reaching
as high as Mt = 0.8.

Growth rates of the simulated mixing layers are suppressed with increasing Mach
number as observed experimentally. Also in accord with experiments, the mean velocity
difference across the layer is found to be inadequate for scaling most turbulence
statistics. An alternative scaling based on the mean velocity difference across a typical
large eddy, whose dimension is determined by two-point spatial correlations,
is proposed and validated. Analysis of the budget of the streamwise component of
Reynolds stress shows how the new scaling is linked to the observed growth rate
suppression. Dilatational contributions to the budget of turbulent kinetic energy are
found to increase rapidly with Mach number, but remain small even at Mc = 1.8
despite the fact that shocklets are found at high Mach numbers. Flow visualizations
show that at low Mach numbers the mixing region is dominated by large azimuthally
correlated rollers whereas at high Mach numbers the flow is dominated by small
streamwise oriented structures. An acoustic timescale limitation for supersonically
deforming eddies is found to be consistent with the observations and scalings and is
offered as a possible explanation for the decrease in transverse lengthscale.
Static wall layers in the displacement of two visco-plastic fluids in a plane channel
Authors: ALLOUCHE M. , FRIGAARD I. A. , SONA G.
Published: July 2002

In a plane-channel displacement flow of two visco-plastic fluids, it is possible for
there to be a static residual layer of the displaced fluid left stuck to the walls of
the channel. This phenomenon provides an idealized model for the formation of a
wet micro-annulus, due to poor mud removal, during the primary cementing of an
oil well. Using a lubrication approximation, it is shown that sufficient conditions for
the non-existence of a static wall layer can be computed simply in terms of two
dimensionless parameters: the Bingham number for the displacing fluid (B1) and the
ratio of the yield stresses of the two fluids (ϕY). When these conditions are not met,
it is possible to compute the maximum possible static wall layer thickness hmax, which
depends on B1, ϕY and on a third dimensionless
parameter ϕB, a buoyancy to yield stress ratio.

On computing displacements using the lubrication approximation, the interface is
observed to asymptotically approach the maximum static layer thickness as t → ∞.
Results from fully two-dimensional displacement computations are also presented.
These indicate that the displacement front propagates at a steady speed along the
channel, leaving behind a static layer which is significantly thinner than hmax. Surprisingly,
the computed static layer thickness is observed to decrease with a parametric
increase in the dimensionless yield stress of the displaced fluid. To explain these results
we analyse the streamline configuration close to a steadily advancing displacement
front. We demonstrate heuristically that the local visco-plastic dissipation functional
will be approximately minimized by a critical layer thickness at which the displaced
fluid begins to recirculate ahead of the displacement front. Comparison of the critical
recirculation limit with the static layer thickness computed from the fully transient
model gives a very close agreement, suggesting that a form of energy minimization is
responsible in this case for selecting the static layer thickness.
One-point turbulence structure tensors
Authors: KASSINOS S. C. , REYNOLDS W. C. , ROGERS M. M.
Published: July 2002

The dynamics of the evolution of turbulence statistics depend on the structure of
the turbulence. For example, wavenumber anisotropy in homogeneous turbulence is
known to affect both the interaction between large and small scales (Kida & Hunt
1989), and the non-local effects of the pressure–strain-rate correlation in the one-point
Reynolds stress equations (Reynolds 1989; Cambon et al. 1992). Good quantitative
measures of turbulence structure are easy to construct using two-point or spectral
data, but one-point measures are needed for the Reynolds-averaged modelling of
engineering flows. Here we introduce a systematic framework for exploring the role of
turbulence structure in the evolution of one-point turbulence statistics. Five one-point
statistical measures of the energy-containing turbulence structure are introduced and
used with direct numerical simulations to analyse the role of turbulence structure
in several cases of homogeneous and inhomogeneous turbulence undergoing diverse
modes of mean deformation. The one-point structure tensors are found to be useful
descriptors of turbulence structure, and lead to a deeper understanding of some rather
surprising observations from DNS and experiments.
Wave formation on a shallow layer of flowing grains
Authors: PRASAD SHYAM N. , PAL DIPANKAR , RÖMKENS MATHIAS J. M.
Published: July 2002

The phenomenon of longitudinal waves in shallow grain flows has been studied
through laboratory experiments. The transport process of spherical particles on a
metallic chute has been characterized for this purpose. The wave mode of material
transport could be measured within selected combinations of flow parameters such as
the angular inclination of the chute, the mean size of the grains and the mass flow rate.
It has been observed that the moving particles tend to redistribute systematically in the
direction of mean flow. As a result, nonlinear longitudinal waves evolve on the surface
of the chute. Observations of the predominantly rolling mode of particle motion
revealed significant particle dispersion away from the wavefronts. The frequency of
inter-particle collisions was low in the dispersed flow regions but increased rapidly
near the wavefronts to dissipate the excess kinetic energy, thus resulting in a large
increase in the average volumetric solid fraction. In order to explain the appearance of
discontinuities in the volumetric solid fraction, a theoretical model that preserves the
overall balance of energy and allows a discontinuous periodic solution is examined
here. The depth-averaged dispersed flow of the grains has been approximated by
equations of motion similar to those of shallow fluid flow. The resistance to the
rolling motion of the particles is expressed in terms of the hydrodynamic drag force.
The theoretical model predicts the flow criterion for which the longitudinal waves
would be self-sustaining.
Kinematic dynamo action in large magnetic Reynolds number flows driven by shear and convection
Authors: PONTY YANNICK , GILBERT ANDREW D. , SOWARD ANDREW M.
Published: July 2002

A numerical investigation is presented of kinematic dynamo action in a dynamically
driven fluid flow. The model isolates basic dynamo processes relevant to field generation
in the Solar tachocline. The horizontal plane layer geometry adopted is chosen as
the local representation of a differentially rotating spherical fluid shell at co-latitude
ϑ; the unit vectors [xcirc ], ŷ and zˆ
point east, north and vertically upwards respectively.
Relative to axes moving easterly with the local bulk motion of the fluid the rotation
vector Ω lies in the (y, z)-plane inclined at an angle
ϑ to the z-axis, while the base of
the layer moves with constant velocity in the x-direction. An Ekman layer is formed
on the lower boundary characterized by a strong localized spiralling shear flow. This
basic state is destabilized by a convective instability through uniform heating at the
base of the layer, or by a purely hydrodynamic instability of the Ekman layer shear
flow. The onset of instability is characterized by a horizontal wave vector inclined at
some angle ∈ to the x-axis. Such motion is two-dimensional, dependent only on two
spatial coordinates together with time. It is supposed that this two-dimensionality
persists into the various fully nonlinear regimes in which we study large magnetic
Reynolds number kinematic dynamo action.

When the Ekman layer flow is destabilized hydrodynamically, the fluid flow that
results is steady in an appropriately chosen moving frame, and takes the form of a
row of cat's eyes. Kinematic magnetic field growth is characterized by modes of two
types. One is akin to the Ponomarenko dynamo mechanism and located close to some
closed stream surface; the other appears to be associated with stagnation points and
heteroclinic separatrices.

When the Ekman layer flow is destabilized thermally, the well-developed convective
instability far from onset is characterized by a flow that is intrinsically time-dependent
in the sense that it is unsteady in any moving frame. The magnetic field is concentrated
in magnetic sheets situated around the convective cells in regions where chaotic particle
paths are likely to exist; evidence for fast dynamo action is obtained. The presence
of the Ekman layer close to the bottom boundary breaks the up–down symmetry of
the layer and localizes the magnetic field near the lower boundary.
Response of a circular cylinder wake to superharmonic excitation
Authors: BAEK SEUNG-JIN , LEE SANG BONG , SUNG HYUNG JIN
Published: July 2002

A systematic numerical analysis is performed for superharmonic excitations in a
wake where a circular cylinder is rotationally oscillated in time. Emphasis is placed
on identifying the secondary and tertiary lock-on in the forced wakes. The frequency
responses are scrutinized by measuring the lift coefficient (CL). A direct numerical
simulation has been conducted to portray the unsteady dynamics of wake flows
behind a circular cylinder. The Reynolds number based on the diameter is Re = 106,
and the forcing magnitude is 0.10 [les ] Ωmax [les ] 0.40. The tertiary lock-on is observed,
where the shedding frequency (St0) is one third of the forcing frequency (Sf), i.e.
the 1/3 subharmonic lock-on. The phase shift of CL with respect to the forcing
frequency is observed. It is similar to that of the primary lock-on. However, in
the secondary superharmonic excitation, modulated oscillations are observed, i.e. the
lock-on does not exist. As Ωmax increases, St0 is gradually shifted from the natural
shedding frequency (St*0) to lower values. The magnitudes and phases of Sf and St0
are analysed by the phase diagram. The vorticity contours are employed to examine
the vortex formation mode against the forcing conditions.
Numerical study of convection in the horizontal

Bridgman configuration under the action of a

constant magnetic field. Part 1. Two-dimensional flow
Authors: BEN HADID HAMDA , HENRY DANIEL , KADDECHE SLIM
Published: July 2002

Studies of convection in the horizontal Bridgman configuration

were performed to

investigate the flow structures and the nature of the convective regimes

in a rectangular

cavity filled with an electrically conducting liquid metal when it is

subjected to a

constant vertical magnetic field. Under some assumptions analytical

solutions were obtained for the central region and for the turning

flow region. The validity of the solutions was checked by comparison

with the solutions obtained by direct numerical simulations. The

main effects of the magnetic field are first to decrease the strength of

the convective flow and then to cause a progressive modification of the

flow structure

followed by the appearance of Hartmann layers in the vicinity of the

rigid walls. When the Hartmann number is large enough,

Ha > 10, the decrease in the velocity

asymptotically approaches a power-law dependence on Hartmann number. All

these features are dependent on the dynamic boundary conditions, e.g.

confined cavity or cavity with a free upper surface, and on the type

of driving force, e.g. buoyancy and/or thermocapillary forces.

From this study we generate scaling laws that govern

the influence of applied magnetic fields on convection. Thus, the

influence of various flow parameters are isolated, and succinct

relationships for the influence of magnetic

field on convection are obtained. A linear stability analysis was

carried out in the case

of an infinite horizontal layer with upper free surface. The results

show essentially that

the vertical magnetic field stabilizes the flow by increasing the

values of the critical

Grashof number at which the system becomes unstable and modifies

the nature of the instability. In fact, the range of Prandtl number

over which transverse oscillatory

modes prevail shrinks progressively as the Hartmann number is

increased from zero to 5. Therefore, longitudinal oscillatory modes

become the preferred modes over a large range of Prandtl

number.
Axisymmetric flow between differentially rotating

spheres in a dipole magnetic field
Authors: KLEEORIN N. , ROGACHEVSKII I. , RUZMAIKIN A. , SOWARD A. M. , STARCHENKO S.
Published: July 2002

Constant-density electrically conducting fluid is confined to

a rapidly rotating spherical shell and is permeated by an

axisymmetric potential magnetic field with dipole

parity; the regions outside the shell are rigid insulators. Slow steady
axisymmetric

motion is driven by rotating the inner sphere at a slightly

slower rate. Linear solutions

of the governing magnetohydrodynamic equations are derived in the small
Ekman

number E-limit for values of the Elsasser number Λ

less than order unity. Attention

is restricted to the mainstream outside the Ekman–Hartmann

layers adjacent to the inner and outer boundaries.
Convection in a rotating cylindrical annulus.

Part 4. Modulations and transition to chaos at low Prandtl numbers
Authors: HERRMANN J. , BUSSE F. H.
Published: July 2002

Thermal Rossby waves driven by centrifugal buoyancy in a

rotating cylindrical fluid

gap become unstable right at the onset of convection when the Prandtl number

is small. The Benjamin–Feir–Newell instability leads

to modulated thermal Rossby

waves which can also be described by a generalized Ginzburg–Landau
equation. A

resonance instability occurs at a finite distance in

Rayleigh number from the neutral

curve. It leads to two independent wave patterns propagating past each
other and

finally gives rise to vacillations of the amplitude of convection. Most

of these features

can be described to a good approximation by a system of three coupled amplitude

equations. Time integrations based on a Galerkin expansion show transitions
to

chaotic convection at higher Rayleigh numbers.
On the shape of flames under strong acoustic forcing: a mean flow

controlled by an oscillating flow
Authors: DUROX D. , BAILLOT F. , SEARBY G. , BOYER L.
Published: July 2002

A conical flame, in the presence of high-frequency (≈1000 Hz)

and high-amplitude

acoustic modulation of the cold gases, deforms to a shape which is approximately

hemispherical. It is shown that the acoustic level required to

produce a hemispherical

flame is such that the ratio of acoustic velocity to laminar combustion

velocity is about

3. This flame flattening is equivalent to the phenomenon of acoustic restabilization

observed for cellular flames propagating in tubes. The transition between
the conical

flame and a hemispherical flame is described. The surface area of

the reaction zone of

the flame is found to be unmodified when the flame flattens. The velocity

field at the

burner outlet is examined with and without a flame. The mean flow lines
are strongly

deflected when the hemispherical flame is present. We show that the presence
of the

flame creates an unusual situation where the oscillating flow

controls the geometry of the mean flow.
Stabilization of a cylindrical capillary bridge far

beyond the Rayleigh–Plateau limit using acoustic

radiation pressure and active feedback
Authors: MARR-LYON MARK J. , THIESSEN DAVID B. , MARSTON PHILIP L.
Published: July 2002

A novel method of suppressing the Rayleigh–Plateau capillary

instability of a cylindrical liquid bridge is demonstrated which uses the

radiation pressure of an ultrasonic

wave to control the shape of the bridge. The shape of the bridge is

optically sensed and the information used to control the spatial distribution
of

the radiation stress on

the surface of the bridge. The feedback is phased so as to suppress

the growth of the

axisymmetric mode which normally becomes unstable when the slenderness,
given by

the length to diameter ratio, exceeds π. Stabilization is achieved

out to a slenderness

of 4.3 for a bridge density matched to the surrounding water bath in a
Plateau tank.

Breakup of such long bridges was found to produce a satellite drop from
the receding

thread of liquid. The active stabilization mechanism used may have application
to

other capillary systems.
Compositional convection in the presence

of rotation
Authors: ELTAYEB I. A. , HAMZA E. A.
Published: July 2002

The stability of a compositionally buoyant plume, of circular

cross-section, rising in

a rotating infinite fluid is investigated. Both plume and fluid

have the same non-zero

kinematic viscosity, ν, and thermal diffusivity, κ.

The growth rate of the instability

depends on the Taylor number, Ta (which is a dimensionless

number measuring the

effect of the Coriolis force relative to the viscous force) and on

the thickness, s0, of

the plume in addition to the Prandtl number,

σ(=ν/κ) and the Reynolds number,

R (which measures the strength of the forcing). The analysis

is restricted to the case

of small R. It is found that the presence of rotation

enhances instability. A simple

model of a single interface separating the two parts of an infinite

fluid is investigated

first in order to isolate the mechanism responsible for the increase

in the growth rate

with rotation. It is shown that the Coriolis force interacts with the

zonal velocity

component to produce a velocity component normal to the interface.

For the right

choice of wave vector components, this normal velocity component is

in phase with

the displacement of the interface and this leads to instability.

The maximum growth

rate is identified in the whole space of the parameters σ,

Ta, s0 when R[Lt ]1. While

the maximum growth rate is of order R2 in the

absence of rotation, it is increased

to order R in the presence of rotation. It is also found

that the Prandtl number, σ,

which has a strong influence on the growth rate in the absence of

rotation, plays a subservient role when rotation is present.
Vortex generation by line plumes in a rotating stratified fluid
Authors: BUSH JOHN W. M. , WOODS ANDREW W.
Published: July 2002

We present the results of an experimental investigation of the generation of coherent
vortical structures by buoyant line plumes in rotating fluids. Both uniform and
stratified ambients are considered. By combining the scalings describing turbulent
plumes and geostrophically balanced vortices, we develop a simple model which
predicts the scale of the coherent vortical structures in excellent accord with laboratory
experiments.

We examine the motion induced by a constant buoyancy flux per unit length B,
released for a finite time ts, from a source
of length L into a fluid rotating with angular
speed Ω = f/2. When the plume discharges into a uniformly stratified environment
characterized by a constant Brunt–Väisälä frequency,
N>f, the fluid rises to its level
of neutral buoyancy unaffected by the system rotation before intruding as a gravity
current. Rotation has a strong impact on the subsequent dynamics: shear develops
across the spreading neutral cloud which eventually goes unstable, breaking into a
chain of anticyclonic lenticular vortices. The number of vortices n emerging from the
instability of the neutral cloud,
n = (0.65±0.1)Lf1/2/
(t1/2sB1/3),
is independent of the
ambient stratification, which serves only to prescribe the intrusion height and aspect
ratio of the resulting vortex structures. The experiments indicate that the Prandtl ratio
characterizing the geostrophic vortices is given by
P = Nh/(fR) = 0.47±0.12; where
h and R are, respectively, the half-height and radius of the vortices.
The lenticular vortices may merge soon after formation, but are generally stable and persist
until they are spun-down by viscous effects.

When the fluid is homogeneous, the plume fluid rises until it impinges on a free
surface. The nature of the flow depends critically on the relative magnitudes of the
layer depth H and the rotational lengthscale
Lf = B1/3/f.
For H>10Lf, the ascent
phase of the plume is influenced by the system rotation and the line plume breaks
into a series of unstable anticylonic columns of characteristic radius
(5.3±1.0)B1/3/f
which typically interact and lose their coherence before surfacing. When
H<10Lf, the
system rotation does not influence the plume ascent, but does control the spreading of
the gravity current at the free surface. In a manner analogous to that observed in the
stratified ambient, shear develops across the surface current, which eventually becomes
unstable and generates a series of anticyclonic surface eddies with characteristic radius
(1.6±0.2)B1/3t1/3s
/f2/3. These surface eddies are significantly more stable than their
columnar counterparts, but less so than the lenticular eddies arising in the uniformly
stratified ambient.

The relevance of the study to the formation of coherent vortical structures by leads
in the polar ocean and hydrothermal venting is discussed.
Stability of multiple steady states of convection in laterally heated cavities
Authors: GELFGAT A. YU. , BAR-YOSEPH P. Z. , YARIN A. L.
Published: July 2002

A parametric study of multiple steady states, their stability, onset of oscillatory instability,
and some supercritical unsteady regimes of convective flow of a Boussinesq fluid in
laterally heated rectangular cavities is presented. Cavities with four no-slip boundaries,
isothermal vertical and perfectly insulated horizontal boundaries are considered. Four
distinct branches of steady-state flows are found for this configuration. A complete
study of stability of each branch is performed for the aspect ratio A (length/height)
of the cavity varying continuously from 1 to 11 and for two fixed values of the
Prandtl number: Pr = 0 and Pr = 0.015. The results are represented as stability
diagrams showing the critical parameters (critical Grashof number and the frequency
at the onset of the oscillatory instability) corresponding to transitions from steady
to oscillatory states, appearance of multi-roll states, merging of multiple states and
backwards transitions from multi-roll to single-roll states. For better comparison
with the existing experimental data, an additional stability study for varying Prandtl
number (0.015 [les ] Pr [les ] 0.03) and fixed value
of the aspect ratio A = 4 was carried out.
It was shown that the dependence of the critical Grashof number on the aspect ratio
and the Prandtl number is very complicated and a very detailed parametric study
is required to reproduce it correctly. Comparison with the available experimental
data for A = 4 shows that the results of a two-dimensional stability analysis are in
good agreement with the experimental results if the width ratio (width/height) of the
experimental container is sufficiently large. The study is carried out numerically with
the use of two independent numerical approaches based on the global Galerkin and
finite-volume methods.
Increased mobility of a surfactant-retarded
bubble at high bulk concentrations
Authors: WANG YANPING , PAPAGEORGIOU DEMETRIOS T. , MALDARELLI CHARLES
Published: July 2002

We study theoretically the adsorption of surfactant onto the interface of gas bubbles
in creeping flow rising steadily in an infinite liquid phase containing surface-active
agents. When a bubble rises in the fluid, surfactant adsorbs onto the surface at the
leading edge, is convected by the surface flow to the trailing edge and accumulates and
desorbs off the back end. This transport creates a surfactant concentration gradient
on the surface that causes the surface tension at the back end to be lower than that at
the front end, thus retarding the bubble velocity by the creation of a Marangoni force.
In this paper, we demonstrate numerically that the mobility of the surfactant-retarded
bubble interface can be increased by raising the bulk concentration of surfactant. At
high bulk concentrations, the interface saturates with surfactant, and this saturation
acts against the convective partitioning to decrease the surface surfactant gradient.
We show that as the Péclet number (which scales the convective effect) increases,
larger concentrations are necessary to remobilize the surface completely. These results
lead to a technologically useful paradigm where the drag and interfacial mobility of
a bubble can be controlled by the level of the bulk concentration of surfactant.
Turbulence cascade and dynamical exchange between spatial scales
Authors: HONORÉ CYRILLE , GRÉSILLON DOMINIQUE
Published: July 2002

The information exchange dynamics between different spatial scales of a turbulent
field is experimentally investigated, with particular reference to the energy cascade
process. This is done by use of the collective light scattering (CLS) diagnostic, a
new optical setting tuned for the observation of atomic number density fluctuations
at macroscopic scales. A two-channel scattering device is described that provides
simultaneously the fluctuations at two different spatial scales. The turbulent system is
an axisymmetric air jet. With this system, time correlations between signal amplitudes
for two different scales show a characteristic time width. This time does not depend on
the observed scales: it is close to the turbulence production time. Nevertheless, signal
amplitude autocorrelation shows a shorter characteristic time. The autocorrelation
time scaling law behaves almost like the eddy turnover time from Kolmogorov theory.
Conversion and onomasiological theory
Authors: VALERA SALVADOR
Published: July 2002

Pavol štekauer,A theory of conversion in English.
Frankfurt am Main: Peter Lang, 1996. Pp. 155.

When, in 1891, Henry Sweet (1891–98, I: 38–40) used the term CONVERSION
for the process that today is also known as ZERO-DERIVATION, he was
probably not aware of the debate that the description of this process would
still raise one century later.

štekauer's book bears witness to a renewed interest in conversion. Such an
interest partly stems from the fact that it is a simple (or, at least, apparently
so), extremely productive process, but also because it remains a challenge to
descriptive linguistics. How conversion operates, what its limits are, how
converted units should be categorised in the study of morphology and lexis,
and even what its real nature is are still open questions despite the attention
given to this issue ever since Sweet's grammar.

This book meets some of these questions in the framework of an
onomasiological theory, which will be briefly discussed below. The book
consists of nine chapters, a section for notes and another for references. The
introduction (chapter 1, pp. 11–13) justifies the work and outlines the
structure of the book. The remaining eight chapters deal with the description
of conversion in the literature (chapter 2, pp. 15–22), its interpretation as
zero-derivation (chapter 3, pp. 23–43), the onomasiological theory and
conversion (chapter 4, pp. 45–53), phonological variation (chapter 5, pp.
55–95), the use and semantic range of converted units (chapter 6, pp.
97–113), proper nouns and conversion (chapter 7, pp. 115–126), directionality
(chapter 8, pp. 127–133), and the productivity of conversion (chapter 9, pp.
135–141).
Conflict or symbiosis? Disentangling farmer-herdsman
relations: the Mossi and Fulbe of the Central Plateau, Burkina Faso
Authors: Breusers Mark , Nederlof Suzanne , Van Rheenen Teunis
Published: July 2002

Conflicts between farmers and herdsmen are certainly not new
phenomena: they already occurred at the time of the biblical
patriarchs. In West Africa, conflicts over the use of scarce natural
resources between farmers and herdsmen are said to be on the
increase. The occurrence of such conflicts is generally attributed to
growing pressure on natural resources, caused by population increase,
the growth of herds and the extension of cultivated areas outpacing
population growth. That such conflicts appear to oppose two ethnic
groups – generally Fulbe herdsmen versus a population group
of
farmers – is explained by the fact that not only has overall competition

over natural resources increased due to a saturation of space, but that

at the same time a balance between the two groups has been broken.
The convergence of production systems, as a result of farmers engaging

in cattle breeding and herdsmen in agriculture, entailed the disappearance

of both ecological and economic complementarity between
the two groups – a process that is said to have been accelerated
by the
droughts of the 1970s and 1980s. The interpretation of these conflicts

depends on the – sometimes implicit – assumption that formerly,
in an
often unspecified epoch in the past, relations between farmers and
herdsmen could be conceived of in terms of symbiosis – a relationship

based on mutual dependence and mutual advantage with implied
complementarity in the ecological and economic spheres.
Two-field transport models for magnetized plasmas
Authors: GARCIA O. E.
Published: July 2002

Two-field fluid models for low-frequency density and electrostatic potential
fluctuations in a purely toroidal magnetized low-β plasma are discussed. In particular,
we present some simple models suitable for investigating plasma transport
close to marginal stability. For gradient-driven fluctuations, linear normal mode
analysis of the interchange and resistive drift wave instabilities are reviewed, with
attention to the relative phase and amplitude of density and electrostatic potential
fluctuations. This reveals many characteristic features of drift-wave fluctuations
that are also observed in laboratory experiments and during ionospheric irregularities.
Finally, these results are used to investigate the nonlinearly conserved energy
functionals, discussing the effect of magnetic field curvature and particle collisions
on energy, enstrophy, and cross-correlation between density and vorticity fluctuations.
Implications for turbulent fluctuations and nonlinear transport in laboratory
and ionospheric plasmas are discussed.
Chickasaw
Authors: Gordon Matthew , Munro Pamela , Ladefoged Peter
Published: July 2002

Chickasaw is a Muskogean language spoken in south-central Oklahoma. Published descriptions of Chickasaw phonetics include Munro & Willmond (1994), Munro (to appear), and Gordon et al. (2000). The following description is a summary of the principal phonetic aspects of Chickasaw drawn primarily from these works.
A new species of Cerapopsis Della Valle (Amphipoda: Isaeidae) from the Atlantic coast of Morocco
Authors: Menioui M. , Myers Alan A.
Published: July 2002

A new species of Cerapopsis (Cerapopsis takamado) is described from the Atlantic coast of Morocco. The genus Cerapopsis, synonymized with Photis Kröyer for nearly a quarter of a century is re-established and now known to contain two species.
Horny sponges from the north-eastern coast of Papua New Guinea, Bismark Sea
Authors: Pulitzer-Finali G. , Pronzato R.
Published: July 2002

A small collection of horny sponges from the north-eastern coast of Papua New Guinea is recorded. It consists of 19 specimens belonging to ten species, of which three are new: Thorectaxia papuensis, Chelonaplysilla delicata, Anomoianthella lamella. Thorectaxia is proposed as a new genus in the family Thorectidae.
Field and laboratory measurement of heart rate in a tropical limpet, Cellana grata
Authors: Chelazzi Guido , Williams Gray A. , Gray Dave R.
Published: July 2002

Heart rate of the tropical limpet Cellana grata was monitored on the shore (Cape d'Aguilar, Hong Kong) and in the laboratory using a non-invasive technique. Individual field measurements performed on inactive limpets, in a variety of thermal conditions during a diurnal low tide, showed a general increase in heart rate with increasing body temperature. This relationship was not always evident when monitoring individual responses over a diurnal low tide period, since under some circumstances, heart rate of individuals decreased with increasing the temperature of the substrate and foot. A factorial laboratory experiment showed that heart rate was faster at higher temperatures but slower in larger animals. The combined evaluation of field and laboratory data suggests that limpets in some habitats may be able to regulate their metabolic rate when resting on hot rock substrates.
Prolonged settlement and prediction of recruitment in two sympatric intertidal Chthamalus species from south-west Ireland
Authors: Power Anne-Marie , Delany Jane , Myers Alan A. , O'Riordan Ruth M. , McGrath David
Published: July 2002

Attached cypris larvae and less than one month old metamorphs of Chthamalus stellatus and C. montagui (Crustacea: Cirripedia) were sampled from random quadrats on two shores in County Cork, Ireland, from July 1996 to June 1997. Cyprids of C. stellatus were much more abundant than those of C. montagui, but the relative abundance of metamorphs of the two species did not differ significantly. Cyprid abundance predicted metamorph recruitment intensity during peak settlement in C. stellatus but not in C. montagui.
Paul in Pamphylia (Acts 13.13–14a; 14.24b–26): A Critical Note
Authors: CAMPBELL DOUGLAS A.
Published: July 2002

Acts states in 13.13–14a that Paul sailed on his outward journey from Paphos in Cyprus to Pergê in Pamphylia (Περγη), proceeding then to Pisidian Antioch – literally, Antioch-towards-Pisidia. (Pamphylia is the westernmost of two alluvial coastal shelves on the south coast of present-day Turkey; a relatively self-contained geographical area.) Acts states that John-Mark left for Jerusalem from this point after a disagreement, and also does not mention the coastal port of Attaleia (‘Ατταλεια), present-day Antalya. On the return journey, however, noted in 14.24–26a, the remaining missionaries are said to preach in Pergê and then proceed to Attaleia, from which point they sail on to Syrian Antioch, presumably actually disembarking at Seleucia. Now this all looks a little odd at first glance, especially since Pergê is some distance inland for any arrival on the first leg of this journey, and most interpreters have reacted accordingly. I want to suggest here, however, that the author's comments about these two traverses through Pamphylia, although brief and initially a little puzzling, are deliberately asymmetrical, and it is this that betrays their almost certain accuracy in historical terms.
Parasite (Schistosoma mansoni) and host (Biomphalaria glabrata) genetic diversity: population structure in a fragmented landscape
Authors: SIRE C. , LANGAND J. , BARRAL V. , THÉRON A.
Published: July 2002

Random amplified polymorphic DNA (RAPD) markers were used to quantify genetic diversity within and between 5 populations ofSchistosoma mansoniwithin its definitive host (Rattus rattus) and the 5 corresponding populations of the snail intermediate host (Biomphalaria glabrata) from a limited endemic area of murine schistosomiasis on the island of Guadeloupe. Analysis of molecular variance (AMOVA) and canonical correspondence analysis (CCA) were used to test the significance of genetic differentiation between populations. Both methods gave similar results. Of total gene diversity, 15.1% (AMOVA) and 18.8% (CCA) was partitioned between localities forS. mansoniwith an absence of association between genetic and geographical distances. Geographical localities accounted for 20.5% (CCA) of the total diversity forB. glabratapopulations. The genetic distances between pairs of parasite populations were not correlated with the genetic distances between the corresponding pairs of snail host populations. Such strong patterns of local differentiation of both parasite and snail populations are consistent with predictions based on metapopulation dynamics and may have implications on host–parasite susceptibility relationship through local adaptation processes.
Regulation of infrapopulations of Cryptocotyle lingua on

cod
Authors: LYSNE D. A. , HEMMINGSEN W. , SKORPING A.
Published: July 2002

To study the infection dynamics of metacercariae of the digenean

Cryptocotyle lingua, wild living Atlantic cod, Gadus

morhua, were caged for 18 months close to the shore. Here they were
exposed to

naturally occurring transmission stages

of the parasite. First, both the abundance and the variance to mean ratio
of

metacercariae increased, but during the second

half of the study the abundance levelled out, and the variance to mean
ratio

showed a significant decrease. Host mortality

was negligible throughout the study. Based on the relationship between
pigment

spots and metacercariae observed by skin

digestion, there was no indication of density-dependent parasite mortality.
We conclude

that the infrapopulations of

metacercariae on the caged cod probably were regulated by density-dependent
host responses

acting against the cercariae.
Egg production in adult trematodes: adaptation or

constraint?
Authors: POULIN R.
Published: July 2002

Parasite life-history traits should reflect past environmental

and host-related selective pressures acting to produce

strategies that maximize transmission success. The evolution of adult body

size and egg production in 804 species of

trematode parasites was investigated using independent contrasts derived
from

a phylogeny of trematodes. Contrasts in

trematode body size were positively correlated with contrasts in egg size,

and almost significantly correlated with contrasts

in numbers of uterine eggs. After controlling for body size, no relationship

existed between egg size and egg numbers,

suggesting that there is no trade-off between the two components of egg

production. Average host body mass and latitude

of the sampling site did not correlate with either trematode body size
or

egg size. Contrasts between trematode taxa

exploiting ectotherm hosts and their sister taxa exploiting endotherms

showed no consistent difference in either body size

or egg size. The effect of other variables on trematode life-histories,

such as the nature of the habitat in which eggs are

released, the site of attachment within the host's body, or the number
of

hosts involved in the life-cycle, could not be

evaluated statistically. The similarity in life-history traits among

members of given clades suggests that phylogenetic

constraints may have acted to limit or mask any adaptive changes expected

from changes in host-related or environmental conditions.
The protein antigens secreted in vivo by adult male

Schistosoma mansoni
Authors: CUTTS L. , WILSON R. A.
Published: July 2002

Adult schistosomes can be transferred surgically from donor

C57BL/6 mice to the portal veins of naive recipients with

complete success. This procedure bypasses larval development and the

antibody response of the host is directed against,

and can be used to identify, those antigens released only by viable,

mature parasites. Serum collected from the recipient

mice (WTS) was used in Western blotting studies to probe fractionated

parasite protein. Twelve immunodominant

proteins were identified, ranging in molecular weight from 14 to 208 kDa.

The magnitude of the IgG response against each

antigen could be divided into 2 categories, on the basis of optical

densitometry of the blots. In addition, defined parasite

fractions were probed with WTS by Western blotting, in order to

determine the relative abundance and distribution of

each antigen in schistosome tissue. To confirm and expand on these

initial observations, oligospecific polyclonal antibody

for each immunogen was affinity purified from Western blots; it was

then used in immunocytochemistry to identify the

sources of secretion for 8 of the 12 antigens, at the cellular level.

From the results, it appeared that after the transfer of

adult worms, the first antibodies detected were mostly directed against

the gastrodermis. At later times additional reactivity

was expressed against the tegumental membrane. These differences probably

reflect the relative abundances of the gut and tegumental secretory

products.
Geographical genetic structure within the human lung
fluke, Paragonimus westermani, detected from DNA sequences
Authors: BLAIR D. , AGATSUMA T. , WATANOBE T. , OKAMOTO M. , ITO A.
Published: July 2002

Nucleotide sequences were obtained for the second internal transcribed
spacer of the ribosomal gene repeat and for part
of the mitochondrial cytochrome c oxidase subunit I gene
from geographical isolates of Paragonimus westermani from
Japan, China, Korea, Taiwan, the Philippines, peninsular Malaysia and Thailand.
Sequences were obtained from several
other species of Paragonimus for comparative purposes. Two
groups were recognized within P. westermani: an NE group
(China, Japan, Korea, Taiwan) which was relatively uniform and included
both diploid and triploid forms, and a southern
group (Malaysia, Thailand, Philippines), members of which were genetically
distant from one another. According to both
ITS2 and COI data, genetic distances among P. westermani isolates
equalled or exceeded those between some distinct
species of Paragonimus. The ITS2 sequences were conserved
relative to COI sequences. Substitutions among the latter
may be approaching saturation within the genus Paragonimus.
Malaria toxins from P. chabaudi chabaudi AS and
P. berghei ANKA cause dyserythropoiesis in C57BL/6 mice
Authors: RUDIN W. , QUESNIAUX V. , FAVRE N. , BORDMANN G.
Published: July 2002

The lack of correlation between parasitaemia and anaemia in severe
malaria indicates that factors in addition to schizont
rupture or erythrophagocytosis contribute to anaemia. We asked whether
malaria
toxin (MT) from Plasmodium berghei
or P. chabaudi might impair erythropoiesis. Daily intraperitoneal
injection of MT into C57BL/6 mice induced a transient
reduction of RBC values by 25–30% after about 2 weeks, followed
by increased haematopoiesis in the spleen as compared
to mice receiving uninfected RBC preparations. There was a 3 (P.
berghei) to 8-fold (P. chabaudi) increase of total
proliferative activity in the spleen. Flow cytometric analyses showed that
this was accompanied by some differentiation
of TER-119 positive erythroid cells and of Gr-1 positive myeloid cells.
Erythroid
and myeloid progenitor cell-derived
colony assays confirmed these results and revealed an increase in the number
of CFU-E ([les ]200-fold), BFU-E ([les ]10-fold)
and CFU-GM ([les ]20-fold) in the spleen of MT treated mice, as compared
to controls.
Role of the immune response induced by superantigens in
the pathogenesis of microbial infections
Authors: MAILLARD I. , LUTHI F. , ACHA-ORBEA H. , DIGGELMANN H.
Published: July 2002

Superantigens (SAgs) are microbial proteins which have potent effects
on
the immune system. They are presented by
major histocompatibility complex (MHC) class II molecules and interact

with a large number of T cells expressing specific
T cell receptor Vβ domains. Encounter of a SAg leads initially to
the
stimulation and subsequently to the clonal deletion
of reactive T cells. SAgs are expressed by a wide variety of microorganisms

which use them to exploit the immune system
to their own advantage. Bacterial SAgs are exotoxins which are linked to

several diseases in humans and animals. A classical
example is the toxic shock syndrome in which the massive release of
cytokines by SAg-reactive cells is thought to play
a major pathogenic role. The best characterized viral SAg is encoded by

mouse mammary tumour virus (MMTV) and
has proved to have a major influence on the viral life cycle by dramatically

increasing the efficiency of viral infection. In
this paper, we review the general properties of SAgs and discuss the
different types of microorganisms which produce
these molecules, with a particular emphasis on the role played by the
SAg-induced immune response in the course of microbial infections.
Segregation of a microsporidian parasite during host cell mitosis
Authors: TERRY R. S. , DUNN A. M. , SMITH J. E.
Published: July 2002

We investigated the segregation of an intracellular microsporidian
parasite during host cell division. A time-course
experiment was carried out to examine the distribution of parasites relative
to host chromosomal DNA via light and
electron microscopy. Fluorescent light microscopy and EM studies showed
that the parasite lay in the perinuclear zone
of the host cell during interphase and segregated to daughter cells at
mitosis. At metaphase, the parasite was frequently
closely associated with host microtubules and mitochondria. Electron-dense
bridges were observed between the parasites
and the host microtubules and also between host mitochondria and microtubules.
The study suggests that both the parasite
and the host cell organelles segregate in association with spindle microtubules.
Overview and significance of molecular methods: what role
for molecular epidemiology?
Authors: THOMPSON R. C. A. , CONSTANTINE C. C. , MORGAN U. M.
Published: July 2002

In this chapter, the contribution of molecular tools in understanding the aetiology and ecology of infectious diseases is
examined in the context of molecular epidemiology (ME). ME is seen as providing the ‘tools’, both laboratory and
analytical, which have predictive significance in epidemiological investigations of the causation of disease. A diversity of
questions can be addressed with these tools which can conveniently be viewed as particular regions of DNA and grouped
according to the different hierarchical levels of specificity by which infectious agents can be characterized. These groupings
and the applications of the different molecular tools are described, and consideration given to the most appropriate methods
of analysing data from ME investigations.
Coccidiosis in the European badger (Meles meles) from
England, an epidemiological study
Authors: ANWAR M. A. , NEWMAN C. , MACDONALD D. W. , WOOLHOUSE M. E. J. , KELLY D. W.
Published: July 2002

In total 445 faecal samples were collected from 259 European badgers (Meles meles) in Wytham Woods, Oxfordshire, UK
(462080). Microscopical examination revealed infection with 2 species of coccidia Eimeria melis and Isospora melis. From
the initial examination of each animal, point prevalence rates of 0·44 and 0·35 were calculated for Eimeria and Isospora
respectively. The intensity of infection was significantly greater for Eimeria than Isopora and the distribution of intensities
was highly skewed for both species, with a few individuals shedding the majority of oocysts. Incidence and recovery rates
for both coccidia species were calculated from longitudinal data collected at 3-monthly intervals from a subset of the adult
badger population, and the predicted prevalence rates based on these were similar to the point prevalence rates. This
suggests little, if any, parasite-induced mortality in the adult population. In contrast, there was a marked and significant
reduction in the point prevalence and intensity of infection with Eimeria from cub to adult badger suggesting a degree of
acquired immunity to Eimeria melis on initial exposure and/or that there is significant Eimeria-associated mortality in the
cub population. No such relationship was found for Isospora infection. In those adult badgers with co-infections there was
a direct relationship between the intensity of Eimeria and Isospora. The taxonomic status of these parasites suggests a
heteroxenous life-cycle for I. melis, and direct transmission of E. melis. However, the greater than expected prevalence of
co-infection is consistent with a common source of infection, such as communal latrines.