bluuebunny/crossref_metadata_2025 huggingface dataset:
Laboratory and numerical studies of baroclinic

waves in an internally heated rotating fluid

annulus: a case of wave/vortex duality?
Authors: READ P. L. , LEWIS S. R. , HIDE R.
Published: July 2002

The structure, transport properties and regimes of flow exhibited
in

a rotating fluid

annulus, subject to internal heating and sidewall cooling, are studied
both in the

laboratory and in numerical simulations. The performance of the numerical
model

is verified quantitatively to within a few per cent in several cases by
direct

comparison with measurements in the laboratory of temperature and horizontal

velocity

fields in the axisymmetric and regular wave regimes. The basic azimuthal
mean flow

produced by this distribution of heat sources and sinks leads to strips
of potential

vorticity in which the radial gradient of potential vorticity changes sign
in

both the

vertical and horizontal directions. From diagnosis of the energy budget
of numerical

simulations, the principal instability of the flow is shown to be predominantly

baroclinic in nature, though with a non-negligible contribution towards
the

maintenance

of the non-axisymmetric flow components from the barotropic wave–zonal
flow

interaction. The structure of the regime diagram for the internally heated
baroclinic

waves is shown to have some aspects in common with conventional wall-heated

annulus waves, but the former shows no evidence for time-dependence in
the form

of ‘amplitude vacillation’. Internally heated flows instead

evidently prefer to make

transitions between wavenumbers in the regular regime via a form of vortex
merging

and/or splitting, indicating a mixed vortex/wave character to the

non-axisymmetric

flows in this system. The transition towards irregular flow occurs via
a form of

wavenumber vacillation, also involving vortex splitting and merging events.

Baroclinic eddies are shown to develop from an initial axisymmetric flow
via a mixed

sinuous/varicose instability, leading to the formation of detached
vortices

of the same

sign as the ambient axisymmetric potential vorticity at that level, in
a

manner which

resembles recent simulations of atmospheric baroclinic frontal instability

and varicose

barotropic instabilities. Dye tracer experiments confirm the mixed wave/vortex

character of the equilibrated instabilities, and exhibit chaotic advection
in

time-dependent flows.
Miscible displacement between two parallel

plates: BGK lattice gas simulations
Authors: RAKOTOMALALA N. , SALIN D. , WATZKY P.
Published: July 2002

We study the displacement of miscible fluids between two parallel
plates,

for different

values of the Péclet number Pe and of the viscosity ratio

M. The full Navier–Stokes

problem is addressed. As an alternative to the conventional finite

difference methods,

we use the BGK lattice gas method, which is well suited to

miscible fluids and allows

us to incorporate molecular diffusion at the microscopic scale of the lattice.
This

numerical experiment leads to a symmetric concentration profile about the
middle

of the gap between the plates; its shape is determined as a function of
the

Péclet

number and the viscosity ratio. At Pe of the order of 1, mixing

involves diffusion and

advection in the flow direction. At large Pe, the fluids do not

mix and an interface

between them can be defined. Moreover, above M∼10, the interface

becomes a well-defined finger, the reduced width of which tends to

λ∞=0.56 at large values of

M. Assuming that miscible fluids at high Pe are similar
to

immiscible fluids at high

capillary numbers, we find the analytical shape of that finger, using an

extrapolation of

the Reinelt–Saffman calculations for a Stokes immiscible flow.

Surprisingly, the result

is that our finger can be deduced from the famous Saffman–Taylor
one,

obtained in a potential flow, by a stretching in the flow direction by

a factor of 2.12.
Diffusive turbulence in a confined jet experiment
Authors: RISSO FRÉDÉRIC , FABRE JEAN
Published: July 2002

An experimental analysis of the turbulence in an axisymmetrical
jet

within a closed

tube is presented. At some distance from the nozzle, a turbulent region

develops, where

the kinetic energy of the mean flow almost vanishes. In this region, the

turbulence is

transported by turbulent diffusion and its energy decreases with the distance

from the

inlet. A complete description of the flow field has been achieved using
laser

Doppler

anemometry. Some unusual features are highlighted: the statistical moments
of the

velocity decay exponentially, the integral length scales remain constant,
the radial

profiles are self-similar and the Reynolds stress tensor is isotropic and
homogeneous

in the radial direction. These results highlight the roles of pressure

fluctuations and

any mean residual motion in the return to isotropy.
An axisymmetric free surface with a 120 degree angle along a circle
Authors: VANDEN-BROECK J.-M. , KELLER JOSEPH B.
Published: July 2002

An axisymmetric flow due to a submerged sink in water of

infinite depth is considered,

with a stagnation point on the free surface above the sink.

Forbes & Hocking (1990)

calculated numerically a flow for each value of the Froude number

F smaller than a

critical value Fc. For F close to

Fc there is a ring-shaped bump on the free
surface.

At F=Fc, the crest of the bump

becomes a ring of stagnation points. We use the

numerical procedure of Hocking & Forbes to show that the bump is the
first crest

of a train of axisymmetric waves. The wave amplitude decreases with increasing

distance from the source. Then we give a local analysis of axisymmetric
free-surface

flows with a circular ring of stagnation points. We find flows in which
the surface

has a discontinuity in slope with an enclosed angle of 120°

all along the ring. This

behaviour is consistent with the numerical solution for

F=Fc near the crest of the bump.
The response of sheared turbulence to changes in curvature
Authors: CHEBBI B. , HOLLOWAY A. G. L. , TAVOULARIS S.
Published: July 2002

Transversely homogeneous, uniformly sheared, turbulent flow was
allowed to reach its
asymptotic structure in a straight wind tunnel section and then it was
passed through
a sequence of two curved sections and a final straight section. The cross-sectional

shape of the entire wind tunnel was rectangular, while the two curved sections
had
circular centrelines with the same radius but opposing curvatures. In all
cases, the
mean strain rate due to curvature was relatively weak (±5%), compared
to the mean
shear rate, but its effects on the turbulence kinetic energy and structure
were substantial;
streamwise pressure gradient effects were negligible. The turbulence structure

approached approximately self-similar states towards the downstream ends
of each
curved section but the main interest of the present study was the rate
of adjustment
of the turbulence following a stepwise change in curvature. It has been
shown that the
adjustment of the shear stress anisotropy, which is a sensitive indicator
of structural
changes, can be approximated by a first-order system response, whose time
constant
scales with the inverse mean shear and is independent of the curvature
parameter. Uniformly
sheared flow results were used for an interpretation of the structure of
curved
turbulent boundary layers, both during adjustment and in a fully developed
state.
Stability of hydromagnetic dissipative Couette flow
with non-axisymmetric disturbance
Authors: CHEN CHA'O-KUANG , CHANG MIN HSING
Published: July 2002

A linear stability analysis has been implemented for hydromagnetic
dissipative Couette
flow, a viscous electrically conducting fluid between rotating concentric
cylinders in the
presence of a uniform axial magnetic field. The small-gap equations with
respect to
non-axisymmetric disturbances are derived and solved by a direct numerical
procedure.
Both types of boundary conditions, conducting and non-conducting walls,
are
considered. A parametric study covering wide ranges of μ, the ratio
of angular velocity
of the outer cylinder to that of inner cylinder, and Q, the Hartmann
number which
represents the strength of axial magnetic field, is conducted. Results
show that the
stability characteristics depend on the conductivity of the cylinders.
For the case of
non-conducting walls, it is found that the critical disturbance is a non-axisymmetric

mode as the value of μ is sufficiently negative and the domain
of Q where non-axisymmetric
instability modes prevail is limited. Similar results are obtained for

conducting walls at low Hartmann number. In addition, the transition of
the onset of
instability from non-axisymmetric modes to axisymmetric modes for the case
μ=−1
with increasing strength of magnetic field are discussed in detail. For
high values of the
Hartmann number, the critical disturbance is always the axisymmetric stationary
mode
for non-conducting walls but not for conducting walls. For
−1[les ]μ<1, it is demonstrated that non-axisymmetric instability

modes prevail in a wide range of Q for
conducting walls and axisymmetric oscillatory modes may, in fact, become
more
critical than both of the non-axisymmetric and axisymmetric stationary
modes at
higher values of the Hartmann number.
Local fluid and heat flow near contact lines
Authors: Anderson D. M. , Davis S. H.
Published: July 2002

Journal of Fluid Mechanics, vol. 268 (1994), pp. 231–265

It has recently come to our attention that our paper, which describes
Marangoni-driven
flow near a contact line, overlooks solutions involving a general thermal

boundary condition on the free surface (private communication, S. J. Tavener
1997).
These new solutions are applicable for non-isothermal flows in a corner
region where
one boundary is a rigid plane (and either perfectly insulating or perfectly
conducting)
and the other is a free surface upon which a general thermal boundary condition
is
applied. We describe these additional solutions below.
The role of surface disturbances in the entrainment of bubbles by
a liquid jet
Authors: OGUZ HASAN N.
Published: July 2002

In this paper, air entrainment by a liquid jet is studied.
The size of bubbles entrained
by jets plunging into a liquid can be consistently decreased
to the 50–100 μm range,
and their number increased in a highly controllable fashion, by surrounding
a mm-size
jet by a hollow cap with a slightly larger inner diameter. When the right
amount
of air is supplied to the cap, small air bubbles detach from a steady annular
cavity
that forms around the jet and are entrained into the liquid. The fluid
mechanical
principles underlying this interesting and useful effect are investigated
experimentally
and theoretically in this paper. It is shown that a key aspect of the process
is the
jet surface roughness, which is studied quantitatively and explained in
terms of the
boundary layer instability inside the nozzle. The maximum bubble size is
found to
be nearly equal to one quarter of the wavelength of the jet surface disturbances,

consistent with a breakup process of relatively large air pockets around
the jet,
as suggested by close-up pictures. The average bubble size downstream of
the cap
increases proportionally to the air to water flow ratio. Boundary integral
simulations
of the air pocket formation are carried out. The results are found to be
useful
in explaining important characteristics of the experiment such as the threshold
for
entrainment and cavity size.
Magnetohydrodynamic flow in precessing
spherical shells
Authors: TILGNER A.
Published: July 2002

Flow in a rapidly rotating, precessing spherical shell is studied
with and without an
applied magnetic dipole field in order to model the Earth's core.
The primary response
of the fluid to precessional forcing is a solid body rotation about an
axis other than
the rotation axis of the shell. The orientation and energy of that flow
is predicted well
by an asymptotic theory. Ekman layers at the boundaries of the shell break
down
at critical latitudes and spawn internal shear layers. The limit of small
precession
rate is investigated in particular: at zero magnetic field, the strongest
shear layers are
inclined at 30° with respect to the rotation axis of the shell and
erupt at 30° latitude
from the inner core. When a magnetic dipole field with its dipole oriented
along the
rotation axis of the shell is applied, shear zones develop additional structure
and
change position and orientation. At an Elsasser number of 10, most flow
structures
tend to align with the rotation axis of the shell.
Observations of ribbing instabilities in
elastic fluid flows with gravity stabilization
Authors: GRILLET ANNE M. , LEE ALEX G. , SHAQFEH ERIC S. G.
Published: July 2002

We have investigated the role of elasticity in the stability of air–fluid interfaces during
fluid displacement flows. Our investigations of the stability of coating flows with
an eccentric cylinder geometry for both a viscous Newtonian fluid and ideal elastic
Boger fluids are discussed in terms of three classes of phenomena. To begin, we
have documented several new features in traditional fingering instabilities in elastic
displacement flows. These include a very strong elastic destabilization of forward
roll coating: a destabilization which can be correlated directly with the elasticity of
the coating fluid and which appears to be present even in the absence of diverging
channel walls. Moreover, elastic effects are shown to create a novel saw-toothed cusped
pattern in the eccentric cylinder roll-and-plate geometry. Secondly, we have found
that purely elastic bulk flow instabilities in the neighbourhood of air–fluid interfaces
can cause surface deformations if the secondary flow is of sufficient strength. Finally,
flows created by the displacement of less viscous air by a more viscous elastic
fluid are found to display a new class of purely elastic instabilities which appear
to be independent of traditional viscous fingering instabilities and elastic bulk flow
instabilities. Thus interfaces which are stable for Newtonian fluids are unstable via
purely elastic mechanisms. We have found that indeed elasticity has a dramatic
effect on the stability of interfaces, not only changing the critical conditions, but
also changing the manifestation of traditional fingering instabilities, and causing new
purely elastic interfacial instabilities.
Transonic flow of moist air around a thin airfoil with non-equilibrium
and homogeneous condensation
Authors: RUSAK ZVI , LEE JANG-CHANG
Published: July 2002

A new small-disturbance model for a steady transonic flow of moist air with
non-equilibrium and homogeneous condensation around a thin airfoil is presented.
The model explores the nonlinear interactions among the near-sonic speed of the
flow, the small thickness ratio and angle of attack of the airfoil, and the small amount
of water vapour in the air. The condensation rate is calculated according to classical
nucleation and droplet growth models. The asymptotic analysis gives the similarity
parameters that govern the flow problem. Also, the flow field can be described by
a non-homogeneous (extended) transonic small-disturbance (TSD) equation coupled
with a set of four ordinary differential equations for the calculation of the condensate
(or sublimate) mass fraction. An iterative numerical scheme which combines Murman
& Cole's (1971) method for the solution of the TSD equation with Simpson's integration
rule for the estimation of the condensate mass production is developed. The
results show good agreement with available numerical simulations using the inviscid
fluid flow equations. The model is used to study the effects of humidity and of energy
supply from condensation on the aerodynamic performance of airfoils.
Control of global instability in a non-parallel near wake
Authors: LEU TZONG-SHYNG , HO CHIH-MING
Published: July 2002

The effect of base suction on a plane wake was found to produce significant changes
in wake dynamics. The wake is produced by merging two boundary layers from the
trailing edge of a splitter plate in a two-stream water tunnel. A threshold suction
speed exists which is approximately equal to half of the free-stream velocity. If the
suction speed is below the threshold, the wake flow is unstable. If the suction speed
is above the threshold, the wake becomes stable and no vortex shedding is observed.
In the present experiment, the suction technique can stabilize a wake at a maximum
tested Reynolds number of 2000.

The suction significantly reduces the length of the absolutely unstable region in
the immediate vicinity of the trailing edge of the splitter plate and produces a non-parallel flow pattern, resulting in the breakdown of global instability. The global
growth rate changes from positive (unstable flow) to negative (stable flow) at the
suction speed equalling 0.46 of the free-stream velocity. The threshold suction speed
can be accurately predicted by the global linear theory of Monkewitz et al. (1993)
with a non-parallel flow correction.
Models of Public Sector Intervention: Providing for the Elderly

in Argentina (c. 1890–1994)
Authors: LLOYD-SHERLOCK PETER
Published: July 2002

This article analyses the role of the public sector in

providing social insurance and assistance to the elderly in Argentina

between the late nineteenth century and the present day. It assesses

the extent to which this involvement embodied clear-cut development

paradigms or was driven by political pressures. Between the 1940s and

1970s the public sector enjoyed a monopoly of insurance and assistance

provision, with the private and voluntary sectors largely excluded.

These monopolies failed to provide satisfactory levels of a welfare

and proved financially unsustainable. By the 1980s a gradual process

of pluralisation had begun, which culminated with the partial

privatisation of social insurance in 1994.
Dynamics of waves and multidimensional
solitons of the Zakharov–Kuznetsov
equation: II. Higher-order calculation;
nonlinear development
Authors: INFELD E. , SKORUPSKI A. A.
Published: July 2002

The Zakharov–Kuznetsov equation describes the propagation of weak ion
acoustic waves in a strongly magnetized plasma. Their dynamics have been studied
in a series of papers, one of which gives growth rates of instabilities found numerically,
as well as pictures of soliton collisions [J. Plasma Phys.64, 397 (2000) –
Part I]. In the present paper, we find good approximate formulas for growth rates
of the dominant instability, vastly improving those of Part I. This is done by proceeding
to higher order in the expansion, combined with an incorporation of exact
values for the boundaries of the unstable region in the formulas. The result is better
than we had any right to expect. We next depart from linear stability analysis and
look at nonlinear dynamics to obtain a pulse in time. The maximum amplitude of
this pulse is seen to be proportional to the linear growth rate, a result that was so
far suspected from numerics but not derived theoretically. (This paper can be read
independently of Part I.)
Kinetic Alfvén solitons in a low-beta plasma
Authors: KALITA B. C. , BHATTA R. P.
Published: July 2002

Kinetic Alfvén solitons with hot electrons and finite electron
inertia in a low-beta (β=8πn0T/B2G,
the ratio of the kinetic to the magnetic pressure) plasma
is studied analytically, with the ion motion being considered dominant
through
the polarization drift. Both compressive and rarefactive kinetic Alfvén
solitons are found to exist within a definite range of
kz (the direction of propagation of
the kinetic Alfvén solitary waves with respect to the direction
of
the magnetic
field) for each pair of assigned values of β and M (Mach
number).
Unlike in
previous theoretical investigations, β appears as an explicit parameter
for the
kinetic Alfvén solitons in this case. In addition, consideration
of
the electron
pressure gradient is found to suppress the speed of both the Alfvén
solitons
considerably for A
(=2QM2/βk2z,
with Q the electron-to-ion mass ratio) less than unity.
Nonlinear effects in Alfvén resonance
Authors: DMITRIENKO I. S.
Published: July 2002

A study is made of the influence of nonlinearity upon the structure
of a
steady-state disturbance brought about by low-frequency
(ω[Lt ]ωi) monochromatic
magnetosound propagating in a transversally inhomogeneous low-pressure
plasma
(β[Lt ]me/mi),
in the vicinity of the Alfvén resonance
point for the case when the principal
linear mechanism for forming the transverse structure is provided by magnetic
field
diffusion due to small plasma resistivity. It is shown that the nonlinear
properties
of the fundamental harmonic of a disturbance are determined by its self-action
through a plasma density variation that it produces. The disturbance structure
in
the region of the Alfvén resonance is described.
Dust-acoustic waves in self-gravitating dusty plasmas with
fluctuating dust charges
Authors: VERHEEST FRANK , SHUKLA P. K. , RAO N. N. , MEURIS PETER
Published: July 2002

It is shown that the recently published work of Pandey and Dwivedi
[J. Plasma
Phys. 55, 395 (1996)] dealing with dust-acoustic
waves in a self-gravitating unmagnetized dusty plasma is erroneous.
This is demonstrated on the basis of a dispersion
relation in which gravitational and electrostatic forces are kept
on an equal footing.
Furthermore, a general linear dispersion relation for the dust-acoustic
and dust-ion
acoustic waves in self-gravitating dusty plasmas is obtained, taking into
account
the dust-charge perturbations. Specific results for limiting cases are
discussed.
Shock waves and rarefaction waves in magnetohydrodynamics. Part 1.
A model system
Authors: MYONG R. S. , ROE P. L.
Published: July 2002

The present study consists of two parts. Here in Part 1, a model
set
of conservation
laws exactly preserving the MHD hyperbolic singularities is investigated
to develop
the general theory of the nonlinear evolution of MHD shock waves. Great
emphasis
is placed on shock admissibility conditions. By developing the viscosity
admissibility condition, it is shown that the intermediate shocks are
necessary to ensure
that the planar Riemann problem is well-posed. In contrast, it turns out
that the
evolutionary condition is inappropriate for determining physically relevant
MHD
shocks. In the general non-planar case, by studying canonical cases, we
show that
the solution of the Riemann problem is not necessarily unique –
in particular, that
it depends not only on reference states but also on the associated internal
structure. Finally, the stability of intermediate shocks is discussed,
and a theory of their
nonlinear evolution is proposed. In Part 2, the theory of nonlinear waves
developed
for the model is applied to the MHD problem. It is shown that the topology
of the
MHD Hugoniot and wave curves is identical to that of the model problem.
Experimental investigation of the propagation

properties of an edge fluctuation in the KT-5C tokamak
Authors: KAN ZHAI , YU-HONG XU , YI-ZHI WEN , CHANG-XUAN YU , WAN-DONG LIU , CHAO WANG , GE ZHUANG , ZHI-ZHAN XU
Published: July 2002

It is found on the KT-5C tokamak that an edge fluctuation can be

excited using

a pair of floating Langmuir-probe pins. This fluctuation propagates along
the

magnetic field, with its amplitude decreasing drastically when it is off
the

magnetic field line, which is similar to the results obtained from experiments
on

the TEXT tokamak. Moreover, our experimental observations indicate that
the

excited fluctuation propagates with the electron directional motion, and
is

mainly manifested in an electron density fluctuation. Physically, this
excited

fluctuation could be considered as modulation of the external electric
field by

electrons, and is carried by the electron directional motion wherever it
goes.

These results are in good agreement with the proposed ballistic model that
can

be derived by solving the linearized Vlasov equation.
Nonlinear stationary magnetoconvection in a rotating fluid
Authors: TAGARE S. G.
Published: July 2002

We investigate finite-amplitude magnetoconvection in a rotating
fluid in the
presence of a vertical magnetic field when the axis of rotation is parallel
to a
vertical magnetic field. We derive a nonlinear, time-dependent, one-dimensional
Landau–Ginzburg equation near the onset of stationary convection
at
supercritical pitchfork bifurcation when

formula here

and a nonlinear time-dependent second-order ordinary differential equation
when
Ta=T*a
(from below).
Ta=T*a
corresponds to codimension-two bifurcation
(or secondary bifurcation), where the threshold for stationary convection
at the
pitchfork bifurcation coincides with the threshold for oscillatory convection
at
the Hopf bifurcation. We obtain steady-state solutions of the one-dimensional
Landau–Ginzburg equation, and discuss the solution of the nonlinear
time-dependent second-order ordinary differential equation.
Exact solutions of the collisional Vlasov
equation
Authors: EL-HANBALY A. M. , ELGARAYHI A.
Published: July 2002

The symmetry group of the Vlasov–Fokker–Planck
equation (VFPE) is
constructed. The effects of the Poisson equation on this group
is studied, and
different types of similarity solutions of the whole system of equations
(VFPE+Poisson equation) are obtained.
Microwave gas discharge produced
and sustained by a surface wave propagating
along a cylindrical metal antenna with a dielectric coating
Authors: AZARENKOV N. A. , DENISENKO I. B. , OSTRIKOV K. N.
Published: July 2002

The structure of a microwave gas discharge produced and sustained
by a surface wave (SW) propagating along a cylindrical metal antenna with a
dielectric coating is studied. The SW that produces and sustains
the microwave gas discharge propagates along an external magnetic field
and has an eigenfrequency in the range between the electron cyclotron
and electron plasma
frequencies. The presence of a dielectric (vacuum) sheath region
separating the
antenna from the plasma is assumed. The spatial distributions of
the produced plasma density, electromagnetic fields, energy flow density,
phase velocity and
reverse skin depth of the SW are obtained analytically and numerically.
A perturbation method for the Vlasov–Poisson system
Authors: LUNDBERG JONAS , FLÅ TOR
Published: July 2002

A perturbation method for the Vlasov–Poisson system is presented.
It is
self-consistent and entirely based on Lie transformations, which are considered
as active
transformations, generating the dynamics of the particle distribution function
in
the space of distribution functions. The main result is a set of three
equations that
forms a good starting point for a wide variety of problems concerning nonlinear

wave propagation. Besides being efficient, the new perturbation method
is systematic
and therefore also suited for the use of computer algebra.
Rayleigh–Taylor modes in the presence of velocity shear and
vortices
Authors: CHAKRABARTI N. , SPATSCHEK K. H.
Published: July 2002

Two-field models for Rayleigh–Taylor modes are investigated.
The changes due to
external velocity shear (without flow curvature) are reviewed, and the
influences
of the various terms in the models are discussed. It is shown that, in
principle,
velocity shear in combination with dissipation leads to the suppression
of linear
Rayleigh–Taylor modes in the long-time limit. The long-wavelength
modes first
seem to be damped; however, later they show an algebraic growth in time,
before
ultimately the exponential viscous damping wins. In general, the amplitudes
become
very large, and therefore the often-quoted stability of Rayleigh–Taylor
modes
in the presence of velocity shear is more a mathematical artefact than
a real physical
process. Vortices, on the other hand, can lead (together with velocity
shear) to
a quite different dynamical behaviour. Because of a locking of the wave
vectors,
pronounced oscillations appear. This effect is demonstrated by a simple
model
calculation. When vortices and velocity shear are generated from linear
instability, the
resulting oscillatory state finally becomes unstable with respect to Rayleigh–Taylor

modes on a long time scale (‘secondary instability’).
Slowly decaying drift turbulence with wave effects
Authors: MANFREDI GIOVANNI
Published: July 2002

The effect of linear waves on the Charney–Hasegawa–Mima model of drift and
geostrophic turbulence is studied numerically for a slowly decaying field. It is shown
that wave effects can reduce the efficiency of nonlinear mode coupling, effectively
‘freezing’ the spectrum to a narrow band in wavenumber space. Selective nonlinear
interactions tend to favour velocities parallel to the direction of propagation of the
waves. Accordingly, anisotropic spectra are observed, steeper in the direction of
wave propagation, and shallower in the perpendicular direction.
Beam stability in strongly magnetized pair plasmas. Part 1
Authors: ROWE G. W. , ROWE E. T.
Published: July 2002

We present a detailed ab initio calculation of wave modes in a strongly
magnetized pair-plasma slab (which we shall refer to as a beam) embedded in a
pair plasma of different number density. We consider a planar geometry and treat
the case of small beam thickness, for which approximate analytical results can
be obtained and compared with numerical calculations. We briefly compare our
results with those found by others in the case of cylindrical geometry as applied in
the context of radio pulsars.
On the effects of viscosity and anisotropic
resistivity on the damping of Alfvén waves
Authors: CAMPOS L. M. B. C. , MENDES P. M. V. M.
Published: July 2002

The equations of magnetohydrodynamics (MHD) are written for
non-uniform viscosity and resistivity – the latter in the cases of Ohmic and
anisotropic resistivity. In the case of Ohmic (anisotropic) diffusivity, there is
(are) one (two) transverse components of the velocity and magnetic field
perturbation(s), leading to a second-order (fourth-order) dissipative Alfvén-
wave equation. In the more general case of dissipative Alfvén waves with
isotropic viscosity and anisotropic resistivity, the fourth-order wave equation
may be replaced by two decoupled second-order equations for right- and left-polarized waves, whose dispersion relations show that the first resistive
diffusivity causes dissipation like the viscosity, whereas the second resistive
diffusivity causes a change in propagation speed. The second resistive diffusivity
invalidates the equipartition of kinetic and magnetic energy, modifies the
energy flux through the propagation speed, and also changes the ratio of
viscous to resistive dissipation. If the directions of propagation and polarization
are equal (i.e. for right-polarized upward-propagating or left-polarized
downward-propagating waves), the magnetic energy increases relative to the
kinetic energy, the resistive dissipation increases relative to the viscous
dissipation, and the total energy density and flux increase relative to the case
of isotropic resistivity; the reverse is the case for opposite directions of
propagation, i.e. upward-propagating left-polarized waves and downward-propagating right-polarized waves, which can lead to the existence of a critical
layer. The role of the viscosity and first and second resistive diffusiveness on the
dissipation of Alfvén waves is discussed with reference to the solar atmosphere.
Nuuchahnulth
Authors: Carlson Barry F. , Esling John H. , Fraser Katie
Published: July 2002

Nuuchahnulth (PHONETICS), often referred to in the literature as Nootka, is a Wakashan language spoken by people living on the west coast of Vancouver Island in British Columbia, Canada. Each of thirteen Nuuchahnulth bands represents a different dialect group. Nitinaht (Diitiidath) is usually included in the Nuuchahnulth group, but it is divergent enough to be considered a separate language. The data in this illustration represent the Ahousaht (PHONETICS) dialect.
Field examination of dispersion patterns of juvenile Iceland scallops (Chlamys islandica) in the northern Gulf of St Lawrence
Authors: Arsenault David J. , Giasson Martin C. , Himmelman John H.
Published: July 2002

The movement of juvenile Iceland scallops, Chlamys islandica, was quantified in an inshore bed in the Mingan Islands, northern Gulf of St Lawrence, to examine whether the size partitioning over depth in this location, increasing scallop size with depth, results from a gradual downslope movement as scallops increase in size. Scallops of 30.0-44.9 mm and 45.0-59.9 mm in shell height were collected using SCUBA, tagged, and released in the centre of two 0.4-km2 grids at 15 m in depth. After 7 d and 48 d, the net distance moved by the scallops from the release points did not vary between the two size groups but varied significantly between grids. The majority of scallops (70-94%) moved downslope and the mean movement vectors were not orientated in the direction of tidal currents, but rather towards increasing depth. The downslope movement of the scallops was possibly explained by more prolonged swimming bouts when scallops swam downslope. The results suggest that the spatial size partitioning of Iceland scallops at this location is caused by a gradual downslope movement as the scallops increase in size. This study provides the first experimental evidence supporting the controversial hypothesis of recruitment into adult scallop populations involving swimming of juveniles from nursery areas.
Wound healing and survival of beheaded chaetognaths
Authors: Duvert Michel , Perez Yvan , Casanova Jean-Paul
Published: July 2002

The observation in natural conditions of headless chaetognaths with healed scars and ripe gonads led us to reproduce this condition experimentally. Histological sections were made on specimens of Sagitta and Spadella at different times after beheading. The muscles contract and the gut closes the wound, so that by the end of the first two hours, the body wall and gut ‘basement membranes’ are in continuity, so restoring the integrity of the body. After two hours, the muscular layer of the body wall is reshaped and closes up the wound; the gut seals off, and a ‘clot’ is evident in the wound area. The benthic Spadella cephaloptera survives some 30 d or more after decapitation. Specimens carrying ripe ova were able to lay them, to mature and fill their seminal vesicles once or twice and to mate with normal mature specimens. Headless chaetognaths must take up nutrients through the integument. It appears that chaetognaths cannot really regenerate head or tail tip.
The egg string attachment mechanism of selected pennellid copepods
Authors: Schram T.A. , Heuch P.A.
Published: July 2002

The anatomy of the hook apparatus that attaches egg strings to the fish parasites Haemobaphes cyclopterina, Lernaeocera branchialis, Lernaeocera lusci, Lernaeenicus sprattae, Sarcotretes scopeli and Pennella balaenoptera (Copepoda: Pennellida) is described and illustrated. The hook rises from a cupulate base, extending posteriorly and anteriorly in the body cavity. The suspension of the apparatus in the trunk of the different species differs, but the function is similar. The hook tip enters the genital antrum, nearly penetrates the proximal end of the egg string, and continues into a notch on the antrum wall. The apex of the egg string acquires a concave depression like the finger end of a glove. In this way the string is mechanically attached inside the female genital segment. The mobile ectoparasites Lepeophtheirus salmonis and Hatschekia hippoglossi have hooks which function similarly, but perforate the strings.
Surveys of the benthic infauna of the Crouch Estuary (UK) in relation to TBT contamination
Authors: Waldock R. , Rees H.L. , Matthiessen P. , Pendle M.A.
Published: July 2002

Fieldwork on the estuary of the River Crouch in Essex between 1987 (when the use of TBT antifouling on boats less than 25 m in length was banned) and 1992 revealed marked increases in the species diversity of sublittoral benthic communities in the areas which had originally been most contaminated with TBT. These increases were mirrored by a decrease in the TBT contamination of the sediments. The bivalve molluscs and amphipod crustaceans showed the most marked increases in abundance and diversity.
Interactions between canopy forming algae in the eulittoral zone of sheltered rocky shores on the Isle of Man
Authors: Jenkins Stuart R. , Norton Trevor A. , Hawkins Stephen J.
Published: July 2002

The distribution and abundance of Ascophyllum nodosum, Fucus serratus and F. vesiculosus were described at four sheltered, rocky shores in the south of the Isle of Man. Canopy removal experiments were performed at mid tide level of one sheltered, canopy dominated shore to investigate the interactions between the dominant canopy alga, Ascophyllum nodosum and the competitively inferior canopy species of Fucus serratus and F. vesiculosus. Ascophyllum was removed from replicated plots, 2×2 m in size, in both winter and summer; the early growth and survival of fucoids in the presence and absence of the Ascophyllum canopy were monitored and the eventual development of a new canopy described. Juveniles of F. serratus originally present beneath the undisturbed canopy of Ascophyllum died following canopy removal but new recruitment resulted in some canopy development, principally in the winter experiment. Fucus vesiculosus, despite being completely excluded from the Ascophyllum zone of all four shores described, dominated the canopy removal plots of both winter and summer experiments. The Ascophyllum canopy did not recover over a five year period of observation, although a considerable increase in the abundance of Ascophyllum juveniles occurred.
Limited population differentiation in the bearded limpet Patella barbara (Gatropoda: Patellidae) along the coast of South Africa
Authors: Ridgway Tyrone M. , Stewart Barbara A. , Branch George M.
Published: July 2002

Patterns of genetic and morphological variation among eight populations of Patella barbara along the coast of South Africa were examined to see whether reported differences in shell morphology and behaviour between the west and east coasts were mirrored by other morphological and/or genetic differences. Morphological analyses of radular structure, gut-loop coiling and sperm microstructure revealed no differences between the populations. Discriminant functions analysis based on shell morphometrics showed major overlap between populations and failed to separate them. Electrophoretic analysis of 17 enzyme loci gave an overall genetic identity (Nei) value of 0.995, a value which lies within the generally accepted range for conspecific populations. In two of the populations, at Dwesa and Arniston, individuals were found to be ‘gardening’ algal resources. At Clovelly, a ‘normal’ form of P. barbara was found on the rocks, whereas a reduced and tall-shelled form occurred on the ascidian Pyura stolonifera, demonstrating phenotypic morphological plasticity. It was concluded that different populations of Patella barbara are both morphologically indistinguishable and genetically homogenous along the coast of South Africa, thus providing good evidence for widespread gene flow.
The Magi as Wise Men: Re-examining a Basic Supposition
Authors: POWELL MARK ALLAN
Published: July 2002

The tradition that identifies Matthew's magi as ‘wise men’ is considered in light of narrative criticism, social history, and Wirkungsgeschichte. An examination of literature relevant to the narrative's setting reveals that Matthew's readers are expected to regard magian learning not as wisdom but as foolishness. Matthew's narrative is prejudiced against scholarship, such that the magi's status as fools is what qualifies them as candidates for divine revelation. The tradition that regards the magi as wise men can be traced to the Renaissance and attributed to an ideological bias that favours a blessing of scholarship.
Plasmodium falciparum: selection of parasite
subpopulations with decreased sensitivity for antibody-mediated growth
inhibition in vitro
Authors: IQBAL J. , SIRIPOON N. , SNOUNOU V. G. , PERLMANN P. , BERZINS K.
Published: July 2002

The chronic, recrudescent nature of malaria has been linked to
antigenic
diversity of the parasite in which protective
immunity against Plasmodium falciparum may be obtained after repeated
exposure to infection during a long time. In this
study we show that parasite populations with decreased sensitivity to
antibody-mediated growth inhibition are readily
generated in vitro. A laboratory strain, F32, was cultured for
long
periods (10–12 weeks) in the presence of suboptimal
inhibitory antibody concentrations. The antibodies used were the human
monoclonal
antibody 33G2 reacting with a linear
epitope of the P. falciparum blood-stage antigen 332 and rabbit
antibodies
to repeat sequences of the blood-stage antigen
Pf155/RESA. Our data indicate that the P. falciparum parasites
adapt
to antibody pressure as reflected by their specifically
decreased sensitivity to growth inhibition. A relative resistance of the
parasite
to growth inhibition mediated by the
antibodies used in the culture developed successively, while the parasite
remained
sensitive to growth inhibition by other
antibodies. When the antibody pressure was removed a successive return
of
sensitivity to growth inhibition developed.
Immunofluorescence did not reveal any significant difference in antigen
expression between the parasite populations.
However, PCR analysis showed that a new population appeared in the parasites
grown
in the presence of mAb 33G2,
while no such change was detected in those grown in the presence of the
rabbit
antibodies. Our data suggest that the
specific decrease in sensitivity to growth inhibition may either be due
to
down-regulation of antigen synthesis or expression
by antibody pressure or, that antibody pressure selects for parasites with
low expression of a specific antigen from a heterogeneous parasite
population.
Characterization of a cDNA-clone encoding Nc-p43,

a major Neospora caninum tachyzoite surface protein
Authors: HEMPHILL A. , FELLEISEN R. , CONNOLLY B. , GOTTSTEIN B. , HENTRICH B. , MÜLLER N.
Published: July 2002

Neospora caninum is an apicomplexan parasite of

veterinary importance which invades many different cell types and tissues.

N. caninum tachyzoites proliferate intracellularly by

endodyogeny. Eventually the massive proliferation of tachyzoites

leads to host cell lysis and the newly formed parasites are released and

invade neighbouring cells. Tachyzoite cell surface

molecules could serve as ligands, mediating host cell adhesion and invasion.

Nc-p43 is a recently identified N. caninum

tachyzoite surface protein which is functionally involved in the

processes leading to host cell invasion in vitro. Affinity-purified

antibodies directed against Nc-p43 were used to screen a

lambda gt22A-cDNA expression library constructed

from N. caninum tachyzoites. The cDNA insert of one immunoreactive

clone was subcloned and expressed in E. coli as

a poly-histidine fusion protein. The identity of the resulting

recombinant antigen termed recNc-p43 was confirmed by

immunoblotting, immunofluorescence and electron microscopy using

affinity-purified antibodies. The sequence of the

cDNA insert encoding recNc-p43 was determined. Analysis of the deduced

amino acid sequence revealed that Nc-p43

exhibited similarity to SAG1 (p30) and SAG3 (p43), 2 major surface antigens
of

Toxoplasma gondii tachyzoites. These

similarities were not reflected on the immunochemical level, since

no cross-antigenicity between SAG1, SAG3 and Nc-p43 was observed.
Immunocytochemical localization of a putative inhibitory
amino acid receptor subunit in the parasitic nematodes
Haemonchus contortus and Ascaris suum
Authors: SKINNER T. M. , BASCAL Z. A. , HOLDEN-DYE L. , LUNT G. G. , WOLSTENHOLME A. J.
Published: July 2002

A rabbit antiserum was raised against a synthetic peptide corresponding

to a region near the N-terminus of the Haemonchus
contortus inhibitory amino acid receptor subunit, HG1. The antiserum

recognized a recombinant form of the N-terminal
domain of the subunit on Western blots and reacted with the ventral nerve
cord of
H. contortus in immunofluorescence
experiments. Immunofluorescence was also detected in specific head neurons
of
H. contortus: these were tentatively
identified as ring motor- and inter-neurons, plus a possible sensory neuron

equivalent to the AQR cell of Caenorhabditis
elegans. In the roundworm Ascaris suum, immunoreactivity

was limited to the muscle arms, the post-synaptic component
of the neuromuscular junction. The possible ligand of receptors containing
the
HG1 subunit is discussed in the light of this expression pattern.
Localization of mouse type 2 Alu sequence in schistosomes
Authors: IMASE A. , KUMAGAI T. , OHMAE H. , IRIE Y. , IWAMURA Y.
Published: July 2002

Localization of the type 2 Alu sequence (B2), a highly repetitive DNA sequence in the mouse genome, was examined by
in situ polymerase chain reaction (in situ PCR) in schistosomes. The signals to the B2 sequence were detected in the
cytoplasm of the tegumental membrane and in the nuclei of the mesenchymal, testicular, ovarian and vitelline cells of 8-
week Schistosoma japonicum. In contrast, it was difficult to detect any signals of this sequence in 8-week S. mansoni,
whereas in 24-week male S. mansoni the signals were observed in the cytoplasm of the tegumental tubercles and in the
nuclei of the mesenchymal and testicular cells. On the other hand, in 24-week female S. mansoni the signals were found
in the nuclei of the mesenchymal, ovarian and vitelline cells but not found in the tegument. On the contrary, no
hybridization band of the B2 sequence was detected in the amplified DNA of 3-week schistosomula of either species.
These observations proved that the host DNA sequences existed in restricted schistosome cells and were accumulated in
the schistosome body during their development.
DNA probes for detection of the fish microsporidians
Microgemma caulleryi and Tetramicra brevifilum
Authors: LEIRO J. , SISO M. I. G. , PARAMÁ A. , UBEIRA F. M. , SANMARTÍN M. L.
Published: July 2002

DNA probes were developed for the detection and identification of 2 microsporidian parasites of marine fishes,
Microgemma caulleryi (infecting the liver of the greater sand-eel, Hyperoplus lanceolatus) and Tetramicra brevifilum
(infecting muscle, intestine and liver of the turbot, Scophthalmus maximus, a commercially important species). The probe-development procedure used is fast and straightforward, and readily applicable to the development of probes for other
microsporidian species. First, genomic DNA of microsporidian spores was isolated and digested with the restriction
enzyme Hind III. The fragments obtained were ligated into the vector pBluescript SK(+) and cloned in Escherichia coli.
Appropriate inserts were identified and then amplified by PCR, using primers specific for regions adjacent to the Hind III
restriction site in the vector sequence (and thus avoiding the need to develop primers specific for the inserts themselves).
The copies were labelled with digoxigenin, for subsequent use as probes, during PCR itself. The specificity of candidate
probes was tested in dot–blot hybridization assays, with the target DNA being (a) genomic DNA of the microsporidian
from which the probe had been obtained, or of another species, (b) the corresponding genomic DNA in the phagemid,
or (c) DNA from the corresponding host tissue. These assays identified a ca 1180 bp probe for M. caulleryi, denominated
C38, and a ca 1363 bp probe for T. brevifilum, denominated F9. Similar assays designed to assess sensitivity indicated
that F9 showed detectable binding to as little as 500 ng of T. brevifilum genomic DNA, and C38 to as little as 125 ng of
M. caulleryi DNA; these results were obtained with detection of DIG by enzyme immunoassay (i.e. using a phosphatase-coupled anti-DIG antibody), and could no doubt be improved if a radioactive labelling and detection system were used.
The probes developed in this study will greatly facilitate detection and identification of M. caulleryi and T. brevifilum in
fish tissues, and may prove useful for identifying possible intermediate hosts used by these species.