bluuebunny/crossref_metadata_2025 huggingface dataset:
Front dynamics and fingering of a driven contact line
Authors: VERETENNIKOV IGOR , INDEIKINA ALEXANDRA , CHANG HSUEH-CHIA
Published: July 2002

Using photographic imaging and dye tracking experiments, we scrutinize
the dynamics
of a contact line when a finite volume of partially wetting fluid is driven
by gravity
to spread over a slightly inclined dry plane. Unlike spreading mechanisms
driven by
molecular forces, gravity-driven spreading over a dry plane is shown to
possess a
characteristic interfacial ‘nose’ that overhangs
the contact line when the film thickness
is in excess of the capillary length. A unique recirculating vortex exists
within the
nose front which spreads at speeds corresponding to capillary numbers in
excess
of 10−2. Our experiments show that fingering from a gravity-driven

straight front occurs when the above nose configuration cannot be sustained
across
the entire front as the film thins and the apparent contact angle θ
reaches
π/2. The fingers retain the nose configuration while
the remaining segments of the front evolve into a
wedge configuration and stop abruptly due to their large resistance to
fluid flow. This
fingering mechanism is insensitive to fluid wettability, noise or surface
heterogeneity.
Via matched asymptotics, we obtain accurate estimates of fingering position
and speed
at θ=π/2 that are in good agreement with measured values.
This new mechanism
is distinct from other instability and sensitivity fingering mechanisms
and can be in
play whenever θ of the straight front approaches
π/2 from above as the film thins.
Natural convection in a horizontal concentric
cylindrical annulus: oscillatory flow and
transition to chaos
Authors: LABONIA G. , GUJ G.
Published: July 2002

An experimental study of transition from steady laminar to chaotic
flow in a horizontal
annulus between concentric cylinders is conducted for
0.90×105[les ]RaL[les ]3.37×105.

Qualitative information on the averaged thermal field is obtained by an
interferometric
method, whereas the kinematics are visualized by using smoke lines. The
transition
from steady to unsteady mono- and multi-periodic regimes is accurately
studied by a
CTA and CCA combined hot-wire technique. Different data analyses are performed

in order to differentiate the forms of transition.
Structure of Taylor cone-jets: limit of low flow rates
Authors: CHERNEY LEONID T.
Published: July 2002

In this paper the structure of the Taylor meniscus and emitted
jet is studied by
perturbation methods in the limit of low flow rates. An asymptotic system
of governing
equations is derived from the basic equations of electrohydrodynamics.
They
rigorously take into account the inertia and viscosity of the liquid as
well as the
surface ion mobility. The solutions to the asymptotic equations in the
meniscus, jet
and surrounding gas regions are found, matched with each other, and applied
to study
distributions of electric and hydrodynamic variables. Such an approach
allows the liquid
velocity, surface charge, and meniscus-jet radius as well as electric potential
inside
and outside the liquid to be calculated. We also derive the theoretical
dependences
of the current carried by the jet and its diameter on the liquid properties
and flow
rate. These dependences are consistent with the scaling laws found experimentally
by
Fernández de la Mora & Loscertales (1994) and data
obtained by Chen & Pui (1997).
Local boundary-layer receptivity to a convected
free-stream disturbance
Authors: DIETZ A. J.
Published: July 2002

An investigation of the local receptivity of a Blasius boundary
layer to a harmonic
vortical disturbance is presented as a step towards understanding boundary-layer

receptivity to free-stream turbulence. Although there has been solid experimental

verification of the linear theory describing acoustic receptivity of boundary
layers,
this was the first experimental verification of the mechanism behind local
receptivity
to a convected disturbance. The harmonic wake from a vibrating ribbon positioned

upstream of a flat plate provided the free-stream disturbance. Two-dimensional
roughness
elements on the surface of the plate acted as a local receptivity site.
Hot-wire
measurements in the boundary layer downstream of the roughness confirmed
the generation
of Tollmien–Schlichting (TS) instability waves by an outer-layer
interaction
between the long-wavelength convected disturbance and the short-scale mean-flow

distortion due to the roughness. The characteristics of the instability
waves were
carefully measured to ensure that their behaviour was correctly modelled
by linear
stability theory. This theory was then used to determine the immeasurably
small
initial wave amplitudes resulting from the receptivity process, from wave
amplitudes
measured downstream. Tests were performed to determine the range of validity
of
the linear assumptions made in current receptivity theories. Experimental
data obtained
in the linear regime were then compared to theoretical results of other
authors
by expressing the experimental data in the form of an efficiency function
which is
independent of the free-stream amplitude, roughness height and roughness
geometry.
Reasonable agreement between the experimental and theoretical efficiency
functions
was obtained over a range of frequencies and Reynolds numbers.
Evolution of two-layer thermohaline systems under surface cooling
Authors: VOROPAYEV S. I. , FERNANDO H. J. S.
Published: July 2002

This paper presents the results of a series of laboratory experiments
aimed at understanding
the processes associated with surface freezing of a two-layer fluid. The

flow configuration consists of a layer of cold, salty water overlying a
relatively deep
bottom layer of warm, saltier water. This situation is common in high-latitude
oceans
during periods of rapid ice formation. The experiments were conducted in
a tank
with well-insulated side and bottom walls, placed in a walk-in freezer
with air
temperatures from −12 to −20°C. A system of thermocouples
was used to measure
the temperatures at fixed levels in water, ice and air. Microscale conductivity
and
temperature probes were used to obtain vertical profiles of temperature
and salinity
in the water. In general, when external uxes of heat and salt are absent,
such a
system enhances static stability, in the sense that the net density difference
between
the layers increases with time. When external uxes of heat (because of
surface cooling)
and salt (rejected during ice formation) are applied, however, this fluid
system
may become unstable and overturning of fluid layers is possible. In addition,
heat
transport from the warmer bottom layer to the colder upper layer may be
important,
possibly leading to a reduction in the rate of ice formation compared to
that
of a homogeneous fluid with temperature and salinity identical to the upper
layer.
Descriptions of such physical processes are given using laboratory experiments,
and
quantitative measurements of salient parameters are compared with the predictions

of a theoretical model developed to explicate the flow evolution.
Linear growth in two-fluid plane Poiseuille flow
Authors: SOUTH M. J. , HOOPER A. P.
Published: July 2002

In recent years a new paradigm has emerged in linear stability
theory due to the
recognition of the importance of non-normality in the Orr–Sommerfeld
equation as
derived from the method of normal modes. For single-fluid flows it has
been shown
that it is possible for the kinetic energy of certain stable mode combinations
to grow
transiently before decaying to zero. We look again at the linear stability
of two-fluid
plane Poiseuille flow in two dimensions, concentrating on transient growth
and its
dependence on the viscosity and depth ratio. The procedure is to solve
the stability
equations numerically and consider disturbances defined as a sum of the
least stable
eigenmodes (not just the least stable interfacial mode). It is found that
the variational
method used to find maximum growth cannot be based upon the kinetic energy

of the flow only and that interface deflection must be included in the
formulation.
We show which modes are necessary for inclusion in the disturbance expression
and
find that the interfacial mode does not make a significant contribution
to possible
energy growth. We examine the magnitude of maximum growth and the nature
of
the disturbances that lead to this growth. The linear energy rate equation
shows that
at moderate Reynolds numbers the mechanism responsible for the largest
two-fluid
growth is transfer of energy from the basic flow via the Reynolds stresses.
The energy
transfer is facilitated by streamline tilting that can be seen at the channel
walls or at
the interface. A similar effect has been found in single-fluid plane Poiseuille
flow.
A study of two-dimensional flow past an oscillating cylinder
Authors: BLACKBURN H. M. , HENDERSON R. D.
Published: July 2002

In this paper we describe a detailed study of the wake structures and flow dynamics

associated with simulated two-dimensional flows past a circular cylinder that is either

stationary or in simple harmonic cross-flow oscillation. Results are examined for

Re=500 and a fixed motion amplitude of ymax/D=0.25.

The study concentrates

on a domain of oscillation frequencies near the natural shedding frequency of the

fixed cylinder. In addition to the change in phase of vortex shedding with respect

to cylinder motion observed in previous experimental studies, we note a central

band of frequencies for which the wake exhibits long-time-scale relaxation oscillator

behaviour. Time-periodic states with asymmetric wake structures and non-zero mean

lift were also observed for oscillation frequencies near the lower edge of the relaxation

oscillator band. In this regime we compute a number of bifurcations between different

wake configurations and show that the flow state is not a unique function of the

oscillation frequency. Results are interpreted using an analysis of vorticity generation

and transport in the base region of the cylinder. We suggest that the dynamics of

the change in phase of shedding arise from a competition between two different

mechanisms of vorticity production.
Control of long-wavelength Marangoni–Bénard convection
Authors: OR A. C. , KELLY R. E. , CORTELEZZI L. , SPEYER J. L.
Published: July 2002

A nonlinear feedback control strategy for delaying the onset and eliminating the
subcritical nature of long-wavelength Marangoni–Bénard convection is investigated
based on an evolution equation. A control temperature is applied to the lower wall
in a gas–liquid layer otherwise heated uniformly from below. It is shown that, if
the interface deflection is assumed to be known via sensing as a function of both
horizontal coordinates and time, a control temperature with a cubic-order polynomial
dependence on the deflection is capable of delaying the onset as well as eliminating the
subcritical instability altogether, at least on the basis of a weakly nonlinear analysis.
The analytical results are supported by direct numerical simulations. The control
coefficients required for stabilization are O(1) for both delaying onset indefinitely and
eliminating subcritical instability. In order to discuss the effects of control, a review is
made of the dependence of the weakly nonlinear subcritical solutions without control
upon the various governing parameters.
Boundary layer entrainment of sand-sized particles at high speed
Authors: BATT R. G. , PETACH M. P. , PEABODY S. A. , BATT R. R.
Published: July 2002

An experimental study of entrainment of sand-sized particles in turbulent
boundary layers has been performed in a high-speed wind tunnel at square-pulse flow
speeds of 27 to 101 ms−1 and for soil bed lengths varying from 2.1 to 5.8 m.
Because of high particle drag-to-weight ratios (D/W = 100–1000) and friction
velocities (uf) well above soil threshold friction velocities
(uft; 10 [les ]
uf/uft [les ] 40), the
present results correspond to the suspension regime of dust lofting, in contrast to
low-speed saltation flows (1 [les ]
uf/uft [les ] 5;
D/W / 15). Results are obtained characterizing
particle entrainment for both a natural soil (White Sands Missile Range
(WSMR) sand; 50% finer-by-weight diameter, D50 = 180 μm)
and a monosized sand sample (Ottawa sand, D50 = 250 μm).
Measurements of local boundary layer velocities and dust densities were performed with
traversing state-of-the-art diagnostics. Scouring rate data
(0.015 [les ] ms [les ] 0.30 g cm−2 s−1)
and streamwise soil flux (10 [les ] Q [les ] 150 g cm−1 s−1)
as a function of bed length and velocity were determined.

Scouring rates were found to increase as the 3/2-power of velocity, but decay as the
inverse square root of dust bed length. Corresponding streamwise soil fluxes (also
known as soil loss rates) increased to the 3/2-power of velocity in contrast to the cube
power dependence for low-speed results
(ufree-stream [les ] 15 m s−1;
Q [les ] 1.5 g cm−1 s−1). Comparison of scouring
rate data (from pre/post-test soil loss measurements) with derived data based on the
rate of change of streamwise flux with distance was
favourable. WSMR rates were always lower than Ottawa sand rates, a result consistent
with the lower repose angle for the Ottawa sand sample.

Both sets of soil data demonstrate that dust edges extend vertically to higher
elevations than corresponding velocity edges. This result implies that the turbulent
Schmidt number for the present flows is less than unity and of the order of 0.7.
Favourable collapsing of the scouring rate data base was achieved when measured
rates were normalized by the friction velocity mass flux, square root of edge Mach
number and sand repose angle ratio. A universal rate of 0.3±0.1 correlated well with
the bulk of the data.
Hysteretic response of supported drops during forced oscillations
Authors: WILKES EDWARD D. , BASARAN OSMAN A.
Published: July 2002

Viscous liquid drops undergoing forced oscillations have been shown to exhibit
hysteretic deformation under certain conditions both in experiments and by solution
of simplified model equations that can only provide a qualitative description of their
true response. The first hysteretic deformation results for oscillating pendant drops
obtained by solving the full transient, nonlinear Navier–Stokes system are presented
herein using a sweep procedure in which either the forcing amplitude A or frequency
Ω is first increased and then decreased over a given range. The results show the
emergence of turning-point bifurcations in the parameter space of drop deformation
versus the swept parameter. For example, when a sweep is carried out by varying Ω
while holding A fixed, the first turning point occurs at
Ω ≡ Ωu as Ω is being increased
and the second one occurs at
Ω ≡ Ωl < Ωu
as Ω is being decreased. The two turning
points shift further from each other and toward lower values of the swept parameter as
Reynolds number Re is increased. These turning points mark the ends of a hysteresis
range within which the drop may attain either of two stable steady oscillatory states –
limit cycles – as identified by two distinct solution branches. In the hysteresis range,
one solution branch, referred to as the upper solution branch, is characterized by
drops having larger maximum deformations compared to those on the other branch,
referred to as the lower solution branch. Over the range
Ωl [les ] Ω [les ] Ωu, the sweep
procedure enables detection of the upper solution branch which cannot be found if
initially static drops are set into oscillation as in previous studies of forced oscillations
of supported and captive drops, or liquid bridges. The locations of the turning points
and the associated jumps in drop response amplitudes observed at them are studied
over the parameter ranges 0.05 [les ] A [les ] 0.125, 20 [les ] Re [les ] 40,
and gravitational Bond number 0 [les ] G [les ] 1. Critical
forcing amplitudes for onset of hysteresis are also
determined for these Re values. The new findings have important ramifications in
several practical applications. First, that
Ωu − Ωl
increases as Re increases overcomes the limitation which is inherent
to the current practice of inferring the surface
tension and/or viscosity of a bridge/drop liquid from measurement of its resonance
frequencies (Chen & Tsamopoulos 1993; Mollot et al. 1993). Moreover, that the value
of A for onset of hysteresis can be as low as 5% of the drop radius, or lower, has
important implications for other free-surface flows such as coating flows.
Numerical investigation of reacting droplets in
homogeneous shear turbulence
Authors: MASHAYEK FARZAD
Published: July 2002

Numerical simulations are performed of a compressible oxidizer gas laden with fuel
droplets. The carrier phase is considered in the Eulerian context and is simulated via
direct numerical simulation (DNS). The fuel droplets are tracked in the Lagrangian
frame and interactions between the two phases are taken into account in a realistic
two-way coupled formulation. It is assumed that combustion takes place in the
vapour phase, resulting in a ‘homogeneous’ reaction described by
fuel + oxidizer → products + energy.
Several simulations are performed within the configuration of
low-Mach-number homogeneous shear turbulence to investigate the effects of the
mass loading ratio, the droplet time constant, the Damköhler number, and the heat
release coefficient. Initial mass loading ratios up to 0.8 and initial Stokes numbers
(based on the Kolmogorov time scale) of 1.23 and 2.46 are considered. The results
of these simulations along with those from non-reacting cases are utilized to analyse
the droplet size distribution, the fuel vapour, the oxidizer, and the reaction rate
and zone. An analysis of the statistics of the two-phase flow indicates that various
fields are accurately resolved and the assumptions invoked in the formulation of the
problem are satisfied. The mean evaporation rate (normalized with the initial mass
of the droplets) decreases with the increase of either the mass loading ratio or the
droplet time constant. It is shown that the droplet size distribution can be reasonably
approximated by a Gaussian probability density function (p.d.f.) for all of the cases.
The joint p.d.f. of the fuel vapour and the oxidizer mass fractions exhibits the features
of a premixed reaction. The values of the Taylor microscale of the fuel vapour and the
oxidizer are closer in the presence of the chemical reaction than in the evaporating but
non-reacting case. The reaction rate exhibits higher values in the regions of the flow
containing the droplets while experiencing moderate increase in the high-strain-rate
regions. The evaporation rate (per mass of the droplet) is smaller for larger droplets
but an opposite trend is observed for the reaction rate. The reaction zone tends to
align with the streamwise direction due to the effects of the mean flow on the droplets.
The alignment is enhanced with either the increase of the mass loading ratio or the
decrease of the droplet time constant, or the decrease of the Damköhler number. The
alignment of the fuel vapour and the oxidizer with the mean flow direction decreases
and increases, respectively, as a result of the chemical reaction.
Control action for stabilizing free shear layers
Authors: FFOWCS WILLIAMS J. E. , MÖHRING W.
Published: July 2002

The possibility of acoustic control of the two-dimensional instabilities of a lossless
plane shear layer of vanishing thickness is studied. The shear layer is formed from a
body of incompressible fluid sliding over another fluid at rest. It is unstable through
the generation of Kelvin–Helmholtz waves. We consider the possibility of adding to
this linearly unstable flow a simple source, driven in such a way that its field interferes
destructively with the instability to render the flow stable. The required strength of
the unsteady control source is determined in terms of the fluctuating velocity at some
fixed position in the moving fluid. We show that no unstable Kelvin–Helmholtz wave
could survive the action of such a source. Next, we examine the scope for constructing
the control signal from a measurement of the flow velocity at some fixed position.
The source is a linear functional of the monitored velocity and we give the transfer
function that would be required for the instabilities to be controlled. We prove that
such control action would completely stabilize the otherwise unstable vortex sheet,
and that other alternative sensor/actuator arrangements could also be effective. We go
on to show that our particular very simple arrangement could not in fact be realized
because, if required to work at all frequencies, it would not be causal. If we insisted
on causality the vortex sheet would then only be stabilized over most frequencies.
That would of course make the controlled flow completely different from the vortex
sheet whose instabilities are so well known – and troublesome. We conjecture that
there will exist some variations of the basic control arrangement described here that
are both physically realizable and effective over the required frequency range. From
our study of the initial value problem we have concluded that short perturbations
would be attenuated very rapidly.
The electrohydrodynamic stability of
a liquid bridge: microgravity experiments
on a bridge suspended in a dielectric gas
Authors: BURCHAM C. L. , SAVILLE D. A.
Published: July 2002

The electrohydrodynamic stability of a liquid bridge was studied in steady and
oscillatory axial electric fields with a novel apparatus aboard a space shuttle. To
avoid interphase transport, which complicates matters in terrestrial, matched-density
systems, the experiments focused on a liquid column surrounded by a dielectric gas.
The micro-gravity acceleration level aboard the spacecraft kept the Bond number
small; so interface deformation by buoyancy was negligible. To provide microgravity
results for comparison with terrestrial data, the behaviour of a castor oil bridge in a
silicone oil matrix liquid was studied first. The results from these experiments are in
excellent agreement with earlier work with isopycnic systems as regards transitions
from a perfect cylinder to the amphora shape and the separation of an amphora into
drops. In addition, the location of the amphora bulge was found to be correlated with
the field direction, contrary to the leaky dielectric model but consistent with earlier
results from terrestrial experiments. Next, the behaviour of a bridge surrounded by a
dielectric gas, sulphur hexa fluoride (SF6), was investigated. In liquid–gas experiments,
electrohydrodynamic ejection of liquids from ‘Taylor cones’ was used to deploy
fluid and form bridges by remote control. Experiments with castor oil bridges in
SF6 identified the conditions for two transitions: cylinder–amphora, and pinch-off.
In addition, new behaviour was uncovered with liquid–gas interfaces. Contrary to
expectations based on perfect dielectric behaviour, castor oil bridges in SF6 could not
be stabilized in AC fields. On the other hand, a low-conductivity silicone oil bridge,
which could not be stabilized by a DC field, was stable in an AC field.
State culture and development in Botswana and Zimbabwe
Authors: Maundeni Zibani
Published: July 2002

This article makes two major claims. The first is that independent Botswana was able to generate and sustain a type of developmental state because of the presence of an indigenous initiator state culture that was preserved by the Protectorate state and was inherited by the post-colonial state elites. The second is that the non-emergence of the developmental state in post-colonial Zimbabwe is explained by the presence of a non-initiator indigenous state culture which was preserved by the Rhodesian colonial state and was inherited by the post-colonial state elites. The article briefly reviews the literature, analyses the Tswana and Shona pre-colonial state cultures, and shows that these were preserved by the colonial states and inherited by the nationalist politicians.
Ethiopia, the Sudan, and Egypt: The Nile River Dispute
Authors: SWAIN ASHOK
Published: July 2002

The Nile flows for 6,700 kilometres through ten countries
in

north-eastern Africa – Rwanda, Burundi, Zaïre/Congo,

Tanzania, Kenya,

Uganda, Eritrea, Ethiopia, the Sudan, and Egypt – before reaching

the Mediterranean, and is the longest international river system in the

world – see Map 1. Its two main tributaries converge at Khartoum:

the White Nile, which originates from Burundi and flows through the

Equatorial Lakes, provides a small but steady flow that is fed by the

eternal snows of the Ruwenzori (the ‘rain giver’) mountains,

while the

Blue Nile, which suffers from high seasonal fluctuations, descends from

the lofty Ethiopian ‘water tower’ highlands. They provide

86 per cent

of the waters of the Nile – Blue Nile 59 per cent, Baro-Akobo (Sobat)

14 per cent, Tekesse (Atbara) 13 per cent – while the contribution

from the Equatorial Lakes region is only 14 per cent.
Generalized dispersive Alfvén waves
Authors: SHUKLA P. K. , STENFLO L.
Published: July 2002

Generalized dispersion relations for Alfvén waves are derived, accounting
for arbitrary values of ω/ωci, k⊥ρi,
and k⊥λe, where ω(ωci) is the
wave (ion gyro) frequency, k⊥ = 2π/λ⊥
the perpendicular (to the external magnetic field line) wavenumber, and
ρi(λe) the ion gyroradius (electron skin depth). Our dispersion
relations are appropriate for deducing the relationships of the dispersive
(inertial and kinetic) Alfvén waves with other plasma modes. The present results
can be considered as a prerequisite for understanding some salient features of the
broadband electromagnetic/electrostatic waves that are frequently observed by the
Freja and FAST spacecraft in the auroral zone of the Earth's ionosphere.
Interaction of a non-symmetric powerful
laser pulse with a plasma
Authors: GARUCHAVA D. P. , MURUSIDZE I. G. , SURAMLISHVILI G. I. , TSINTSADZE N. L. , TSKHAKAYA D. D.
Published: July 2002

The interaction of a powerful non-symmetric laser pulse with
a plasma is studied. The non-symmetry is manifested in an abrupt cut-off of
the rear edge
of the laser pulse compared with its leading edge. At the same time, three
qualitatively different regions are distinguished: the leading edge,
the rear
edge and the region behind the pulse, where it leaves a wake in the form of
generated fields. An analytical solution has been found that defines the
longitudinal accelerating field at the end of the rear edge. The results of
numerical calculations confirm our physical point of view that the
non-symmetry of the laser pulse increases the duration of the ion
channel behind the
front, thereby enhancing the focusing and effective acceleration of
electron bunches.
Instability of isolated three-dimensional magnetic null points
Authors: NÚÑEZ MANUEL
Published: July 2002

Although most magnetic neutral points occurring in nature seem
to form part of a
continuum, recent studies of reconnection have centred on static equilibria
in the
neighbourhood of an isolated three-dimensional null point. The linear stability
of
this configuration is studied here. It is found that one may choose a flux
surface
so that transverse oscillations localized around the surface and polarized
within it
must grow exponentially in time. This means that any static equilibrium
containing
an isolated three-dimensional null point is linearly unstable.
Reply to ‘Comment on “Collective effects in
bremsstrahlung in plasmas” ’
Authors: TSYTOVICH V. N. , BINGHAM R. , de ANGELIS U. , FORLANI A.
Published: July 2002

We reply here to a criticism of our paper (Tsytovich et al.
1996) by Iglesias
(1997).

In our paper we present a very general formulation of collective effects
in
bremsstrahlung that is valid for any non-equilibrium non-Maxwellian particle

distribution. This result is given in (2.20) early in the paper. The standard

treatments of bremsstrahlung found in books like Bekefi (1966) are only
for
thermal plasmas, where the fluctuation–dissipation theorem is valid.
Note that
the fluctuation–dissipation theorem cannot be used for non-thermal
or non-dipole
fields, and in this respect the method we use is more general. Our
method is the more complex of the approaches used, but, as stated, it can

handle situations that cannot be treated by the standard approach. Our
main
result is the formula (2.20), which is valid for any non-equilibrium non-Maxwellian

particle distribution, and which cannot be found anywhere else in
the literature. Furthermore, we find new qualitative effects indicating
that the
ion–ion bremsstrahlung (which is always neglected in the literature)
is not small
in the case where the collective effects are taken into account, and is
in fact, for
certain frequencies, of the order of the electron–electron bremsstrahlung.
The
other qualitatively new result is that, where collective effects are important,
the
electron–electron bremsstrahlung is not of the order
v2Te/c2,

as it is for the case in the absence of collective effects, but of the
order
ω2pe/ω2
times less –
which, for example in the solar interior, where
ω2pe/ω2
is of the order of
v2Te/c2,
is then
of the order of v4Te/c4.
Magnetically confined plasma flows with helical symmetry
Authors: PALUMBO L. J. , PLATZECK A. M.
Published: July 2002

Stationary flows with an ignorable coordinate are analysed and
the differential
equation for the only independent current function of the problem is obtained

for the polytropic, incompressible and adiabatic cases. The possibility
of
confinement for the stationary symmetric plasma fluxes is then investigated

and the confinement conditions are given. Some examples are solved for
the
particular case of helical symmetry; for general flows it is possible to
construct
magnetically confined plasma columns only with cylindrical shape; whereas
if
the plasma velocity has the direction of the ignorable coordinate, we show
that
it is possible to construct magnetically confined plasma columns with helical

shape and plasma flux along the helices.
Joining sheath to plasma in electronegative
gases at low pressures using matched
asymptotic approximations
Authors: BENILOV M. S. , FRANKLIN R. N.
Published: July 2002

The method of matched asymptotic expansions is used to examine
the structure of the plasma sheath of the positive column at low pressure in
electronegative gases using the fluid model to describe the positive-ion motion.
It is shown that at low negative-ion concentrations, and at high concentrations,
the structure is that of a plasma joined to a thin sheath, but that for the
electron/negative-ion temperature ratio
Te/Tn
≡ ε > 5 + √24, and for a well-defined range of
A ≡ nn0/ne0
(the central negative ion to electron density ratio)
and for small Debye length, there is a more complex structure with a central
negative-ion-dominated plasma surrounded by a quasiplasma in which density
oscillations may occur before joining to a sheath. This is in agreement with
recent computations using the same model.
Haemogregarines and other blood infections from deep demersal fish of the Porcupine Seabight, north-east Atlantic
Authors: Davies A.J. , Merrett N.R.
Published: July 2002

Giemsa-stained blood smears were examined from 70 deep demersal fish of 27 species in 20 genera, trawled from depths of 747–4143 m in the region of the Porcupine Seabight, north-east Atlantic. Infections were found in four species of teleosts in three families: 1/3 Alepocephalus rostratus and 1/3 Narcetes stomias (Alepocephalidae); 2/3 Antimora rostrata (Moridae); and 1/1 Cataetyx laticeps (Bythitidae). Blood films from C. laticeps and Antimora rostrata were well preserved but those from the other two species were less satisfactory. The blood parasites included two types of haemogregarines, Haemohormidium-like and viral erythrocytic necrosis (VEN)-like infections. Haemogregarina (sensu lato) johnstoni sp. nov. was described from C. laticeps captured at 1541 m. This haemogregarine was unusual in apparently having dimorphic gamonts, some with prominent caps. A second, but monomorphic, haemogregarine found in Alepocephalus rostratus captured from 985 m, was named as Desseria sp. since only extracellular stages were observed. Haemohormidium-like organisms were found in Antimora rostrata taken from 2441 m, and were similar to those described previously from this deep-sea fish. A VEN-like infection from one N. stomias captured from 2567 m was reported. No marked effects on host cells were evident in any of these blood infections.
Feeding habits of John Dory, Zeus faber, off the Portuguese continental coast
Authors: Silva Alexandra
Published: July 2002

The feeding habits of John Dory (Zeus faber) were studied, based on the analysis of stomach contents from fish sampled in five groundfish surveys. These surveys were carried out off the Portuguese coast during different seasons between 1990 and 1992. The main aspects of feeding biology analysed in this paper are: ontogenetic diet changes, temporal variations in food composition and feeding intensity. Multivariate methods were used to investigate ontogenetic diet shifts. Two main length groups were identified: 8.0–24.9 cm fish, feeding mainly on dragonets and silvery pout, and 25.0–55.9 cm fish whose diet was mainly composed of blue whiting and snipefish. A transitional phase (24.0–30.9 cm fish) with a mixed food composition was observed. This ontogenetic diet shift does not seem to correspond to any important change in body morphology but it does coincide with the onset of sexual maturity in the species.

John Dory switched from a diet of small prey species with more pronounced benthic behaviour to a diet of larger schooling pelagic species. This suggests parallel evolution to more pelagic foraging behaviour. However, John Dory feeding habits appear to be largely controlled by the availability and accessibility of prey species: (i) the diet of adult John Dory is dominated by very abundant species; (ii) shifts in the main prey items between different times of the year and between different areas seem to be related both with their absolute and relative abundance in the environment and with the overlap between the depth distribution of predator and prey.
Grain Marketing Systems in China and India: A Comparative Perspective
Authors: ZHOU ZHANG-YUE
Published: July 2002

It has long been noticed that there is a lack of comparative studies of the economies of China and India. Bardhan (1970) points out that, in numerous textbooks on comparative economic systems, the reader can hardly find any mention of a China-India comparative study, which should be a very important part of any discussion on comparative economic systems in the present world. One reason for this may be the unavailability and unreliability of data, particularly from China. This situation is now changing. A statement prepared by a Delhi-based China Study Group in 1988, clearly points out that ‘it has become possible to secure more reliable data on China, data that can be checked from various sources and collected through field observation’ (Bhattacharjea, Deshingkar, Deshpande, Gupta, Huang, Mohanty, Rao, Tan and Uberoi, 1988).
WHEN IS A HOUSE NOT HOME? DISCIPLES AND FAMILY IN MARK 3.13–35
Authors: PAINTER JOHN
Published: July 2002

The paper provides a study of the disciples and family of Jesus in Mark 3.13–35. It argues, against the prevailing interpretations, that (1) Mark 3.13–35 should be viewed as a subsection of 3.13–6.13, thus 3.20–35 should not be read in isolation from 3.13–19. (2) Recognising the connection of 3.13–19 to 3.22–35 by 3.20–21 points the way to identifying the twelve as those who sought to restrain Jesus. (3) On this basis an outline reading of 3.20–35 is given. Four groups fall under critique here: the twelve, the crowd, the scribes from Jerusalem and the family, the last of these less severely than the other three groups. (4) Family is redefined in terms of discipleship and discipleship in terms of family. (5) The study also argues that, according to Mark, the households of supporters were the strategic centres of the Jesus movement. These are contrasted with synagogues and Temple, which are places of opposition to the Jesus movement.
The public health importance of Ascaris lumbricoides
Authors: O'LORCAIN P. , HOLLAND C.V.
Published: July 2002

Numerous studies have shown that anthelminthic treatment can be effective in improving growth rates when given to malnourished children with ascariasis. Recent investigations have also indicated that Ascaris infections can affect mental processing in some school children. Poor socio-economic conditions are among the key factors linked with higher prevalences of ascariasis, as are defaecation practices, geophagia, cultural differences relating to personal and food hygiene, occupational necessity, agricultural factors, housing style, social class and gender. Chemotherapy is currently the major tool used for the strategic control of ascariasis as a short-term goal. In the long term, improvements in hygiene and sanitation are thought to aid long-term control considerably. Targeted treatment, especially when aimed at schoolchildren, has been a major focus of recent control efforts in some areas. Universal treatment reaches more people and thus decreases further aggregate morbidity, especially in nutritionally vulnerable preschool-age children. Selective treatment requires technical effort to identify heavily infected individuals; acceptance by the community may vary in less educated populations when some individuals receive treatment and others do not. Child-targeted treatment may be more cost-effective than population treatment in reducing the number of disease cases and, in high transmission areas, expanding coverage of a population can be a more cost-effective strategy than increasing the frequency of treatment.
Enrichment and biochemical characterization of
Toxoplasma gondii tachyzoite plasmalemma
Authors: RABJEAU A. , FOUSSARD F. , MAURAS G. , DUBREMETZ J. F.
Published: July 2002

The protozoan parasite Toxoplasma gondii possesses a triple
surface membrane called the pellicle. This is made of an outer
plasmalemma and an inner membrane complex lying under the plasmalemma.
Using a
high salt glycerol treatment
followed by sonication, we have obtained a partial dissociation of the
pellicle.
A plasmalemma-enriched fraction was
isolated on 0·7M sucrose. It was identified by immunodetection
of
the tachyzoite major surface antigens. Protein content,
resolved by SDS–PAGE, revealed that the surface protein SAG1 is the
major component of the plasmalemma. The
plasmalemma fraction is made of small vesicles (20–100 nm) which
possess
a low density (1·085–1·090 g/cm3 in
sucrose)
contrasting with other eukaryotic plasma membranes
(1·12–1·16 g/cm3).
In vitro assessment of the influence of nutrition,
temperature and larval density on trapping of the infective
larvae of Heligmosomoides polygyrus by Arthrobotrys
oligospora, Duddingtonia flagrans and
Monacrosporium megalosporum
Authors: MORGAN M. , BEHNKE J. M. , LUCAS J. A. , PEBERDY J. F.
Published: July 2002

The influence of nutrient level, temperature and larval density
on
the trapping of Heligmosomoides polygyrus L3 by the
nematophagous fungi Arthrobotrys oligospora, Duddingtonia
flagrans and Monacrosporium megalosporum were investigated
by quantification of trapped nematodes. All 3 factors were found to have
a significant effect on the number of larvae
trapped by A. oligospora and M. megalosporum.
Decreased nutrient concentrations resulted in increased trapping for these
2 fungi, but nutrient availability was not found to have a significant
effect on trapping by D. flagrans. The 3 fungi were
found to have similar responses to temperature, with peak trapping
occurring at or near the optimum growth temperatures.
Nematode trapping was found to be density dependent for all 3 fungi,
with increased percentage trapping at increased
larval densities. Comparison in a single experiment of the relative
importance of these factors to each fungus showed that
nutrient level was the main factor influencing trapping by A. oligospora,
whereas D. flagrans and M. megalosporum were
more dependent on larval density.
Schistosoma japonicum and Trichuris suis infections
in pigs fed diets with high and low protein
Authors: JOHANSEN M. V. , BØGH H. O. , GIVER H. , ERIKSEN L. , NANSEN P. , STEPHENSON L. , KNUDSEN K. E. B.
Published: July 2002

The aim of the study was to measure the impact of Schistosoma
japonicum and Trichuris suis infections in young growing
pigs fed low- or high-protein diets. Thirty-two pigs, 6–10 weeks
old, were randomly allocated to 2 groups receiving either
a high- or a low-protein diet. After 11 weeks half of the pigs from
each group were infected with 1500 S. japonicum
cercariae and 4000 T. suis eggs. The weight of the pigs was
measured throughout the study, and blood and faecal samples
were collected every second week from the time of infection. At the time
of infection the low-protein pigs had significantly
lower mean body weights, haemoglobin and albumin levels compared with
the high-protein pigs, and this pattern
continued throughout the study. The serum albumin concentration was
further significantly reduced in the infected low-protein pigs compared
to
the non-infected low-protein pigs. Significantly more S. japonicum
worms as well as faecal and
tissue eggs were found in the low-protein pigs compared with the
high-protein pigs. No differences between the 2 diet
groups were observed in T. suis establishment rates or faecal
egg excretion. We conclude that this low-protein diet increased
the establishment rates of S. japonicum, favoured larger
deposits of S. japonicum eggs in the liver and faecal egg excretion,
reduced weight gains and caused anaemia and hypoalbuminaemia in young
growing pigs as compared with a high-protein diet.
Comparison of richness and diversity of macroparasite
communities among eels from Nova Scotia, the United Kingdom and Australia
Authors: MARCOGLIESE D. J. , CONE D. K.
Published: July 2002

Species richness and diversity of macroparasite assemblages
were compared among American eels (Anguilla rostrata) from
Nova Scotia, European eels (A. anguilla) from the
United Kingdom (Kennedy, Bush & Aho, 1986; Esch et al. 1988;
Kennedy, 1990, 1993), and Australian eels (A. reinhardtii)
from Queensland (Kennedy, 1995). Community richness and
diversity of the macroparasite fauna of American and European eels
did not differ significantly for total parasite component
communities, intestinal parasite component communities, and
intestinal parasite infracommunities. The similarities in
richness and diversity between the parasite communities of American
and European eels are not surprising given the
common, recent origin of these sister species. However, differences
in species composition were noted between Nova
Scotia and the UK. Both species of eels were infected by a nearly
identical suite of specialists, but differences occurred
in the species number and composition of generalist parasites. In
addition, generalist species were rarely dominant in Nova
Scotia, but commonly so in the UK. These differences can be
attributed to the differences in the freshwater fish fauna
and their parasites that occur between Nova Scotia and the UK.
American and European eels are derived from a common
ancestor and, whereas they have carried with them a common suite
of specialist parasites during their brief period of
independence, they acquired different suites of generalists
apparently from their respective continental faunas after they
diverged. In contrast, parasite communities of American and
European eels were significantly less diverse and speciose
than those of Australian eels regardless of scale (total component
community, intestinal component community, intestinal
infracommunity). These results support the notion that parasite
communities have had more time to evolve and/or that
tropical conditions have promoted parasite speciation in Australian eels.
A female-specific cDNA sequence of Schistosoma

mansoni encoding an amidase that is expressed in the

gastrodermis
Authors: SCHÜßLER P. , KÖHRER K. , FINKEN-EIGEN M. , MICHEL A. , GREVELDING C. G. , KUNZ W.
Published: July 2002

A female-specifically expressed cDNA clone was obtained

by screening of a subtractive cDNA library enriched for RNA

from Schistosoma mansoni females. The deduced

protein shows significant homology to a class of enzymes

functioning as amidases. Northern blots revealed a transcript

of 4·0 kb which is absent in larval stages, but is

expressed in adult female

worms. By in situ hybridization, the expression site

of the gene was exclusively localized in the gastrodermis of female

schistosomes. This is the first report of a female-specifically

transcribed sequence of S. mansoni that is not

expressed in the reproductive organs.
The Virtues of Embodiment
Authors: Taliaferro Charles
Published: July 2002

Surprisingly, materialists and dualists often appeal to the same factors in their depiction of being an embodied, human person: sensations, agency, and causal underpinnings. I propose that this picture be expanded to include epistemic, structural, and affective components. I further propose that these elements, taken together, be construed as virtues. Being an embodied, human person consists in the exercise of six types of virtues: Sensory Virtues, the Virtue of Agency, Constitutional Virtues, Epistemic Virtues, Structural Virtues, and Affective Virtues. This project draws on recent contributions to virtue epistemology and to the philosophical analysis of self-respect.
Individual-specific risk factors for anorexia nervosa: a pilot study using a discordant sister-pair design
Authors: KARWAUTZ A. , RABE-HESKETH S. , HU X. , ZHAO J. , SHAM P. , COLLIER D. A. , TREASURE J. L.
Published: July 2002

Background. The aim of this pilot study was to examine which unique factors (genetic and
environmental) increase the risk for developing anorexia nervosa by using a case–control design of
discordant sister pairs.

Methods. Forty-five sister-pairs, one of whom had anorexia nervosa and the other did not, were
recruited. Both sisters completed the Oxford Risk Factor Interview for Eating Disorders and
measures for eating disorder traits, and sib-pair differences. Blood or cheek cell samples were taken
for genetic analysis. Statistical power of the genetic analysis of discordant same-sex siblings was
calculated using a specially written program, DISCORD.

Results. The sisters with anorexia nervosa differed from their healthy sisters in terms of personal
vulnerability traits and exposure to high parental expectations and sexual abuse. Factors within the
dieting risk domain did not differ. However, there was evidence of poor feeding in childhood. No
difference in the distribution of genotypes or alleles of the DRD4, COMT, the 5HT2A and 5HT2C
receptor genes was detected. These results are preliminary because our calculations indicate that
there is insufficient power to detect the expected effect on risk with this sample size.

Conclusions. A combination of intrinsic and extrinsic factors increases the risk of developing
anorexia nervosa. It would, therefore, be informative to undertake a larger study to examine in
more detail the unique genetic and environmental factors that are associated with various forms of
eating disorders.