bluuebunny/crossref_metadata_2025 huggingface dataset:
Shock wave instability and the carbuncle phenomenon: same intrinsic origin?
Authors: ROBINET J.-Ch. , GRESSIER J. , CASALIS G. , MOSCHETTA J.-M.
Published: July 2002

The theoretical linear stability of a shock wave moving in an unlimited homogeneous
environment has been widely studied during the last fifty years. Important results
have been obtained by Dýakov (1954), Landau & Lifchitz (1959) and then by Swan
& Fowles (1975) where the fluctuating quantities are written as normal modes. More
recently, numerical studies on upwind finite difference schemes have shown some
instabilities in the case of the motion of an inviscid perfect gas in a rectangular channel.
The purpose of this paper is first to specify a mathematical formulation for the
eigenmodes and to exhibit a new mode which was not found by the previous stability
analysis of shock waves. Then, this mode is confirmed by numerical simulations which
may lead to a new understanding of the so-called carbuncle phenomenon.
The formation of ‘optimal’ vortex rings, and the efficiency of propulsion devices
Authors: LINDEN P. F. , TURNER J. S.
Published: July 2002

The formation of an axisymmetric vortex ring by forcing uid impulsively through a
pipe is examined. An idealized model of the circulation, impulse and energy provided
by the injected plug is developed, and these quantities are equated to the corresponding
properties of the class of rings with finite cores described by Norbury (1973). It is
shown that, as the length-to-diameter aspect ratio L/D of the plug increases, the size
of the core increases in comparison with all the fluid carried along with the ring, until
the limiting case of Hill's spherical vortex is reached. For aspect ratios larger than a
certain value it is not possible to produce a single ring while conserving circulation,
impulse, volume and energy. This implies that the limiting vortex is ‘optimal’ in
the sense that it has maximum impulse, circulation and volume for a given energy
input. While this matching calculation makes the physical mechanism clear, the L/D
ratio that can be achieved in practice is more appropriately taken from the direct
experimental measurements of Gharib et al. (1998) who concluded that the limiting
value is L/D = 4. This is close to the value found in our calculation.
Fluid-loaded elastic plate with mean flow: point forcing and three-dimensional effects
Authors: GREEN M. R. , CRIGHTON D. G.
Published: July 2002

The unsteady behaviour of an infinitely long fluid-loaded elastic plate subject to
a single-frequency line forcing in the presence of a uniform mean flow is known
to exhibit a number of interesting phenomena. These include the onset of absolute
instability for non-dimensional flow speeds U in excess of some critical speed Uc,
and various interesting propagation effects when U < Uc. In the latter respect Crighton
& Oswell (1991) have shown that over a particular frequency range there exists an
anomalous neutral mode with group velocity directed towards the driver, in violation
of the usual Lighthill outgoing radiation condition. Similar results have been found
by Peake (1997) when transverse curvature effects are included. In this paper we
seek to extend these results and consider the substantially harder problem of a fluid-loaded
elastic plate with uniform mean flow which is subject to a point forcing,
thereby resulting in a two-dimensional structural problem. A systematic method for
determining the absolute instability threshold is developed, and it is shown that the
flow is absolutely unstable for flow speeds U > Uc, where Uc is the one-dimensional
value found by Crighton & Oswell. At flow speeds U < Uc the flow is marginally
stable and convective growth is found to occur downstream of the driver, over a
particular frequency range depending on the transverse Fourier wavenumber ky,
within a wedge-shaped region. Outside this wedge-shaped region there is only neutral
mode behaviour. Asymptotic forms are found for the dominant large-distance causal
flexion response downstream of the driver inside and outside the wedge region, and
the appropriate critical angle for the wedge region is identified. Within the convective
instability wedge the flexion and critical angle take two different forms depending on
whether the frequency ω is greater or less than U2/√5. In addition to this interesting
behaviour, the flow also exhibits the usual anomalous neutral mode behaviour and,
as with Peake's problem, we also find an extra stability (hoop) resulting in neutral
mode behaviour over a small frequency range. Asymptotic forms are also found
for the threshold frequencies which divide up the various regions of stability of the
system (neutral, neutral anomalous, convectively unstable), as a function of ky, and
are compared with the results of both Crighton & Oswell and Peake.
Partial cavity flows. Part 1. Cavities forming on models without spanwise variation
Authors: LABERTEAUX K. R. , CECCIO S. L.
Published: July 2002

Partial cavities that formed on the vertices of wedges and on the leading edge of
stationary hydrofoils were examined experimentally. The geometry of these test objects
did not vary in the spanwise direction (i.e. two-dimensional). Open partial cavities
formed on a series of two-dimensional wedges and on a plano-convex hydrofoil.
These cavities terminated near the point of maximum cavity thickness, and small
vapour-filled vortices were shed in the turbulent cavity wake. The turbulent flow in
the wake of the open cavity was similar to the turbulent shear flow downstream of a
rearward-facing step. Re-entrant flow was not observed in the cavity closure of open
cavities, although recirculating flow associated with a region of flow separation was
detected for some cases. Predictions of a two-dimensional free-streamline model of the
cavitating wedge flows were compared to the experimentally observed cavities. The
model predicted the profile of the open cavity only to the point of maximum cavity
thickness. Examination of the flow field near the closure of the open cavities revealed
adverse pressure gradients near the cavity closure. The pressure gradients around the
open cavities were sufficient to cause large-scale condensation of the cavity. Unsteady
re-entrant partial cavities formed on a two-dimensional NACA0009 hydrofoil. The
interface of the unsteady closed cavities smoothly curved to form a re-entrant jet at
the cavity terminus, and the re-entrant flow was directed upstream. The re-entrant
flow impinged on the cavity interface and led to the periodic production of cloud
cavitation. These cavities exhibited a laminar flow reattachment. The flow around
the closed cavity was largely irrotational, while vorticity was created when the cloud
cavitation collapsed downstream of the cavity. Examination of the flow field near
closure of these cavities also revealed adverse pressure gradients near the partial
cavity closure, but the rise in pressure did not lead to the premature condensation of
the cavity.
Quantities which define conically self-similar free-vortex solutions to the Navier–Stokes equations uniquely
Authors: STEIN CARL FREDRIK
Published: July 2002

It is proved that if, in addition to the opening angle of the bounding conical
streamsurface and the circulation thereon, one of the radial velocity, the radial
tangential stress or the pressure on the bounding streamsurface is given, then a
conically self-similar free-vortex solution is uniquely determined in the entire conical
domain. In addition, it is shown that for ows inside a cone the same conclusion holds
for the Yih et al. (1982) parameter T, but for exterior flows it is shown numerically
that non-uniqueness may occur. For given values of the opening angle of the bounding
conical streamsurface and the circulation thereon the asymptotic analysis of Shtern
& Hussain (1996) is applied to obtain asymptotic formulae which interrelate the
opening angle of the cone along which the jet fans out and the radial tangential stress
on the bounding surface. A striking property of these formulae is that the opening
angle of the cone along which the jet fans out is independent of the value of the
viscosity as long as it is small enough for the first-order asymptotic expressions to
apply. However, these formulae are shown to be inaccurate for moderate values of
the ratio of the circulation at the bounding surface and the viscosity. To amend this
shortcoming, an alternative, more accurate, asymptotic analysis is developed to derive
second-order correction terms, which considerably improve the accuracy.
Excitation of secondary instabilities in boundary layers
Authors: CROUCH J. D.
Published: July 2002

The receptivity to fundamental and subharmonic secondary instabilities

is analysed

for two-dimensional boundary layers. Fundamental modes are excited by the
direct

scattering of Tollmien–Schlichting (TS) waves over surface variations.
The

excitation

of subharmonic modes stems from the combined scattering of acoustic free-stream

disturbances and TS waves over surface variations. The surface variations
are

localized in their streamwise extent and are the result of roughness or
suction.

The

velocity field is expanded in terms of small parameters characterizing
the acoustic

disturbance and the surface variation. The TS wave is included as part
of the base

flow leading to a non-homogeneous system with periodic coefficients governing
the

receptivity. The receptivity amplitudes show a strong dependence on the
TS-wave

amplitude, and for subharmonic modes a strong dependence on the TS-wave
phase at

the location of the surface variation. The receptivity analysis shows a
significant

bias

toward fundamental modes of secondary instability for larger TS-wave amplitudes

– except for conditions of extremely high free-stream sound level.
A

combination

of receptivity results and stability results suggests a bias toward subharmonic
modes

for TS-wave amplitudes below 0.5% and toward fundamental modes for TS-wave

amplitudes above 0.5% (normalized by the local edge velocity).
Trapped modes about multiple cylinders in a channel
Authors: EVANS D. V. , PORTER R.
Published: July 2002

The trapped modes which can occur in a long narrow wave channel

containing any

number of different-sized bottom-mounted circular cylinders arbitrarily
spaced along

the centreline of the channel are considered. The modes, all of which are

antisymmetric

with respect to the centreplane of the channel are of two types: Neumann
modes,

in which the fluid has normal velocity zero on the channel walls corresponding
to

a localized sloshing near the cylinders, and Dirichlet modes, in which
the dynamic

pressure vanishes on the channel walls. These latter modes have no physical
meaning

in the water-wave context but have been observed in a related acoustic
context where

the same governing equations and boundary conditions apply.

It is shown that in general there are [les ]N trapped modes
for any

configuration

of N cylinders, the precise number depending critically on the
geometry

of the

configuration. Both types are of importance in predicting the exciting
forces on

individual cylinders within a large but finite periodic arrangement of
cylinders.
An experimental investigation of the effects of

compressibility on a turbulent reacting mixing layer
Authors: MILLER M. F. , BOWMAN C. T. , MUNGAL M. G.
Published: July 2002

Experiments were conducted to investigate the effect of

compressibility on turbulent

reacting mixing layers with moderate heat release. Side-

and plan-view visualizations

of the reacting mixing layers, which were formed between a

high-speed high-temperature vitiated-air stream and a

low-speed ambient-temperature hydrogen

stream, were obtained using a combined OH/acetone planar

laser-induced fluorescence

imaging technique. The instantaneous images of OH provide

two-dimensional maps of

the regions of combustion, and similar images of acetone,

which was seeded into the

fuel stream, provide maps of the regions of unburned fuel.

Two low-compressibility

(Mc=0.32, 0.35) reacting mixing

layers with differing density ratios and one high-compressibility

(Mc=0.70) reacting mixing layer

were studied. Higher average

acetone signals were measured in the compressible mixing

layer than in its low-compressibility counterpart

(i.e. same density ratio), indicating a lower entrainment

ratio. Additionally, the compressible mixing layer had

slightly wider regions of OH and

50% higher OH signals, which was an unexpected result since

lowering the entrainment

ratio had the opposite effect at low compressibilities. The

large-scale structural changes

induced by compressibility are believed to be primarily

responsible for the difference

in the behaviour of the high- and low-compressibility

reacting mixing layers. It is

proposed that the coexistence of broad regions of OH and

high acetone signals is a

manifestation of a more biased distribution of mixture

compositions in the

compressible mixing layer. Other mechanisms through which

compressibility can affect the combustion are discussed.
Forces on oscillating uniform and tapered cylinders in cross flow
Authors: HOVER F. S. , TECHET A. H. , TRIANTAFYLLOU M. S.
Published: July 2002

Forces are measured at both ends of rigid cylinders with span 60
cm, performing
transverse oscillations within an oncoming stream of water, at Reynolds
number
Re≈3800. Forced harmonic motions and free vibrations of uniform
and tapered
cylinders are studied. To study free motions, a novel force-feedback control
system
has been developed, consisting of: (a) a force transducer, which
measures forces on
a section of a cylinder moving forward at constant speed; (b)
a computer using the
measured force signal to drive in real time a numerical simulation of an
equivalent
mass-dashpot-spring system; (c) a servomotor and linear table
which impose, also in
real time, the numerically calculated motion on the cylinder section. The
apparatus
allows very low equivalent system damping and strict control of the parametric
values
and structure of the equivalent system.

Calculation of the cross-correlation coefficient between forces at the
two ends of the
uniform cylinder reveals five distinct regimes as a function of the nominal
reduced
velocity Vrn: two regimes, for low and high
values of
Vrn, and far away from the
value of VrS corresponding to the Strouhal
frequency,
show small correlation; two regimes immediately adjacent to, but excluding,

VrS show strong correlation, close
to 1; surprisingly, there is a regime containing the Strouhal frequency,
within which
correlation is low. Free vibrations with a 40[ratio ]1 tapered cylinder
show that the regime
of low correlation, containing the Strouhal frequency, stretches to higher
reduced
velocities, while lock-in starts at lower reduced velocities.

When comparing the amplitude and phase of the lift coefficient measured
for free
and then for forced vibrations, we obtain close agreement, both for tapered
and
uniform cylinders. When comparing the cross-correlation coefficient, however,
we find
that it is much higher in the forced oscillations, especially for the uniform
cylinder.
Hence, although the force magnitude and phase may be replicated well in
forced
vibrations, the correlation data suggest that differences exist between
free and forced
vibration cases.
The role of the turbulent scales in the settling
velocity of heavy particles in homogeneous isotropic turbulence
Authors: YANG C. Y. , LEI U.
Published: July 2002

The average settling velocity of heavy particles under a body force
field is studied
numerically in stationary homogeneous isotropic turbulent flows generated
by the
direct numerical simulation and the large eddy simulation of the continuity
and
Navier–Stokes equations. The flow fields corresponding to different
selected ranges of
turbulent scales are obtained by filtering the results of the direct numerical
simulation,
and employed for calculating the particle motion. Wang & Maxey (1993)
showed that
as a consequence of the particle accumulation in the low vorticity region
and the
preferential sweeping phenomenon, the average settling rate in turbulence
is greater
than that in still fluid. In the present study, the phenomenon of particle
accumulation
in the low vorticity region is found to be controlled mainly by the small
scales
with wavenumber kω corresponding
to the maximum of the dissipation (vorticity)
spectrum. However, the increase of the average settling rate,
〈ΔvS〉, also depends
strongly on the large energetic eddies. The small eddies with wavenumber
greater
than 2.5kω have essentially no effect on
the particle accumulation and the average
settling velocity. The large eddy simulation is thus adequate for the present
study
provided the smallest resolved scale is greater than
1/(2.5kω). Detailed calculations
show that 〈ΔvS〉
is maximized and is of order u′/10 when
τp/τk≈1 and
vd/u′≈0.5
for Rλ=22.6–153, where τp

is the particle's relaxation time, τk is the
Kolmogorov
timescale, vd is the settling rate in still
fluid,
u′ is the root mean square of the velocity
fluctuation, and Rλ is the Reynolds number
based on the Taylor microscale.
Receptivity to surface roughness near a swept leading edge
Authors: COLLIS S. SCOTT , LELE SANJIVA K.
Published: July 2002

The formation of stationary cross flow vortices in a three-dimensional
boundary layer
due to surface roughness located near the leading edge of a swept wing
is investigated
using numerical solutions of the compressible Navier–Stokes equations.
The numerical
solutions are used to evaluate the accuracy of theoretical receptivity
predictions which
are based on the parallel-flow approximation. By reformulating the receptivity
theory
to include the effect of surface curvature, it is shown that convex surface
curvature
enhances receptivity. Comparisons of the parallel-flow predictions with
Navier–Stokes
solutions demonstrate that non-parallel effects strongly reduce the initial
amplitude of
stationary cross flow vortices. The curvature and non-parallel effects
tend to counteract
one another; but, for the cases considered here, the non-parallel effect
dominates
leading to significant over-prediction of receptivity by parallel-flow
receptivity theory.
We conclude from these results that receptivity theories must account for
non-parallel
effects in order to accurately predict the amplitude of stationary crossflow
instability
waves near the leading edge of a swept wing.
Saffman–Taylor instability in yield-stress fluids
Authors: COUSSOT PHILIPPE
Published: July 2002

When a fluid is pushed by a less viscous one the well-known Saffman–Taylor

instability phenomenon arises, which takes the form of fingering. Since
this phenomenon is
important in a wide variety of applications involving strongly non-Newtonian
fluids
– in other words, fluids that exhibit yield stress – we undertake
a full theoretical
examination of Saffman–Taylor instability in this type of fluid,
in both longitudinal
and radial flows in Hele-Shaw cells. In particular, we establish the detailed
form of
Darcy's law for yield-stress fluids. Basically the dispersion equation
for both flows is
similar to equations obtained for ordinary viscous fluids but the viscous
terms in the
dimensionless numbers conditioning the instability contain the yield stress.
As a
consequence the wavelength of maximum growth can be extremely small even
at vanishing
velocities. Additionally an approximate analysis shows that the fingers
which are left
behind at the beginning of destabilization should tend to stop completely.
Fingering
of yield-stress fluids therefore has some peculiar characteristics which
nevertheless are
not sufficient to explain the fractal pattern observed with colloidal systems.
Drag reduction of Newtonian fluid in
a circular pipe with a highly
water-repellent wall
Authors: WATANABE KEIZO , UDAGAWA YANUAR , UDAGAWA HIROSHI
Published: July 2002

Drag reduction phenomena, in which 14% drag reduction of tap water
flowing
in a 16 mm-diameter pipe occurs in the laminar flow range, have been clarified.

Experiments were carried out to measure the pressure drop and the velocity
profile
of tap water and an aqueous solution of glycerin flowing in pipes with
highly
water-repellent walls, by using a pressure transducer and a hot-film anemometer,

respectively. The same drag reduction phenomena also occurred in degassed
tap
water when using a vacuum tank. The velocity profile measured in this experiment

gives the slip velocity at the pipe wall, and it was shown that the shear
stress is
directly proportional to the slip velocity.

The friction factor formula for a pipe with fluid slip at the wall has
been obtained
analytically from the exact solution of the Navier–Stokes equation,
and it agrees well
qualitatively with the experimental data.

The main reasons for the fluid slip are that the molecular attraction
between the
liquid and the solid surface is reduced because the free surface energy
of the solid is
very low and the contact area of the liquid is decreased compared with
a conventional
smooth surface because the solid surface has many fine grooves. Liquid
cannot flow
into the fine grooves owing to surface tension. These concepts are supported
by the
experimental result that drag reduction does not occur in the case of surfactant

solutions.
Trapped modes around a row of circular
cylinders in a channel
Authors: UTSUNOMIYA T. , TAYLOR R. EATOCK
Published: July 2002

Trapped modes around a row of bottom-mounted vertical circular cylinders in a
channel are examined. The cylinders are identical, and their axes equally spaced in a
plane perpendicular to the channel walls. The analysis has been made by employing
the multipole expansion method under the assumption of linear water wave theory.
At least the same number of trapped modes is shown to exist as the number of
cylinders for both Neumann and Dirichlet trapped modes, with the exception that
for cylinders having large radius the mode corresponding to the Dirichlet trapped
mode for one cylinder will disappear. Close similarities between the Dirichlet trapped
modes around a row of cylinders in a channel and the near-resonant phenomenon in
the wave diffraction around a long array of cylinders in the open sea are discussed.
An analogy with a mass–spring oscillating system is also presented.
Examination of large-scale structures in a
turbulent plane mixing layer. Part 1. Proper
orthogonal decomposition
Authors: DELVILLE J. , UKEILEY L. , CORDIER L. , BONNET J. P. , GLAUSER M.
Published: July 2002

Large-scale structures in a plane turbulent mixing layer are studied through the use of
the proper orthogonal decomposition (POD). Extensive experimental measurements
are obtained in a turbulent plane mixing layer by means of two cross-wire rakes
aligned normal to the direction of the mean shear and perpendicular to the mean
flow direction. The measurements are acquired well into the asymptotic region. From
the measured velocities the two-point spectral tensor is calculated as a function of
separation in the cross-stream direction and spanwise and streamwise wavenumbers.
The continuity equation is then used for the calculation of the non-measured components
of the tensor. The POD is applied using the cross-spectral tensor as its kernel.
This decomposition yields an optimal basis set in the mean square sense. The energy
contained in the POD modes converges rapidly with the first mode being dominant
(49% of the turbulent kinetic energy). Examination of these modes shows that the
first mode contains evidence of both known flow organizations in the mixing layer, i.e.
quasi-two-dimensional spanwise structures and streamwise aligned vortices. Using the
shot-noise theory the dominant mode of the POD is transformed back into physical
space. This structure is also indicative of the known flow organizations.
Nonlinear dynamics in horizontal film boiling
Authors: PANZARELLA CHARLES H. , DAVIS STEPHEN H. , BANKOFF S. GEORGE
Published: July 2002

This paper uses thin-film asymptotics to show how a thin vapour layer can support
a liquid which is heated from below and cooled from above, a process known as
horizontal film boiling. This approach leads to a single, strongly-nonlinear evolution
equation which incorporates buoyancy, capillary and evaporative effects. The stability
of the vapour layer is analysed using a variety of methods for both saturated and
subcooled film boiling. In subcooled film boiling, there is a stationary solution, a
constant-thickness vapour film, which is determined by a simple heat-conduction
balance. This is Rayleigh–Taylor unstable because the heavier liquid is above the
vapour, but the instability is completely suppressed for sufficient subcooling. A
bifurcation analysis determines a supercritical branch of stable, spatially-periodic
solutions when the basic state is no longer stable. Numerical branch tracing extends
this into the strongly-nonlinear regime, revealing a hysteresis loop and a secondary
bifurcation to a branch of travelling waves which are stable under certain conditions.
There are no stationary solutions in saturated film boiling, but the initial development
of vapour bubbles is determined by directly solving the time-dependent evolution
equation. This yields important information about the transient heat transfer during
bubble development.
The best of all possible words
Authors: MARK ELLISON T. , KLEIN EWAN
Published: July 2002

Diana Archangeli & D. Terence Langendoen (eds.),Optimality Theory: an overview. Malden & Oxford: Blackwell, 1997. Pp. xii + 233.
On the organization and specification of manner features
Authors: DINNSEN DANIEL A.
Published: July 2002

Within feature geometry, different claims have been made about
the range, unity and
location of manner features with little support for a Manner node as a
unit of
subsegmental structure. The issue is reconsidered, drawing on evidence
of interacting
error patterns in the developing systems of three young children acquiring
English.
The results reveal that obstruent stops and glides can serve as targets
of assimilation
when the triggering features are [continuant], [nasal],
or
[approximant], but also block
as targets under superficially similar circumstances. It is argued that
these three
features are dependents of the same node, namely Manner, and that default
features
must be permitted to be both specified and underspecified underlyingly.
Negation, ‘presupposition’ and the
semantics/pragmatics distinction
Authors: CARSTON ROBYN
Published: July 2002

A cognitive pragmatic approach is taken to some long-standing problem
cases of
negation, the so-called presupposition denial cases. It is argued that
a full account
of the processes and levels of representation involved in their interpretation
typically
requires the sequential pragmatic derivation of two different propositions
expressed.
The first is one in which the presupposition is preserved and, following
the rejection
of this, the second involves the echoic (metalinguistic) use of material
falling in the
scope of the negation. The semantic base for these processes is the standard

anti-presuppositionalist wide-scope negation. A different view, developed
by
Burton-Roberts (1989a, b), takes presupposition to be a semantic relation
encoded in natural
language and so argues for a negation operator that does not cancel presuppositions.

This view is shown to be flawed, in that it makes the false prediction
that
presupposition denial cases are semantic contradictions and it is based
on too narrow
a view of the role of pragmatic inferencing.
Smallholder agriculture, wage labour and rural poverty alleviation in land-abundant areas of Africa: evidence from Mozambique
Authors: Tschirley David L. , Benfica Rui
Published: July 2002

This paper challenges the conclusions of earlier writers regarding the roles of smallholder agriculture, commercial agriculture and wage labour in rural poverty alleviation in Mozambique. We review literature from across Sub-Saharan Africa and use recently collected household level data sets to place Mozambique within this literature. Results show that, as in the rest of SSA, wage labour earnings are concentrated among the best-off rural smallholders; these earnings increase income inequality rather than reducing it. Results also suggest that the same set of households, who are substantially better-off than others, has tended to gain and maintain access to the ‘high-wage’ end of the labour market over time. Key determinants of access to ‘high-wage’ labour are levels of education and previously accumulated household wealth. Income from wage labour plays a key role in lifting out of relative poverty those ‘female-headed’ households that can obtain it, yet only about one in five such households earns wage income. We stress that the rural development question in Mozambique, and elsewhere in SSA, should not be framed as an artificial choice between promoting either wage labour opportunities or commercial agriculture or smallholder agriculture. The issue is what mix of approaches is needed to develop a diversified rural economy with growing total incomes, improving food security and rapid reductions in poverty. We suggest that commercial agriculture and increased rural wage labour are important components in any such strategy, but that this strategy will fail without substantial and sustained increases in the productivity and profitability of smallholder agriculture.
Plasma sheath evolution from perturbed electrodes in a negative-ion
plasma
Authors: EL-ZEIN YASSER , YI SEUNGJUN , LONNGREN KARL E. , ALEXEFF IGOR , SHERIDAN TERRENCE E. , HSUAN HULBERT
Published: July 2002

The two-dimensional spatial and temporal evolution of the components
of a plasma
surrounding an electrode whose potential is suddenly decreased is investigated
numerically. The electrode contains a localized convex or a localized concave
voltage perturbation. The quasineutral plasma consists of positive ions
and various
proportions of negative ions and electrons. The results are compared and
contrasted with those obtained with a uniform electrode under identical
plasma conditions.
Alfvén-wave filamentation
Authors: CHAMPEAUX S. , PASSOT T. , SULEM P. L.
Published: July 2002

Transverse focusing or filamentation of weakly nonlinear Alfvén
waves

propagating in a dispersive medium is studied using an amplitude-equation

formalism. Special attention is devoted to the small-β regime, where
kinetic

effects are weak and Alfvén-wave trains are unstable to convective

filamentation. It is shown that, according to their initial duration, focusing
wave

packets can collapse in a finite distance or, conversely, the focusing
can be

arrested by the development of magnetosonic waves, which in both cases
may

lead to the formation of sharp acoustic fronts. This effect, which dominates
the

usual longitudinal steepening, provides an efficient mechanism to heat
the

plasma without requiring large-amplitude waves. It can significantly contribute

to the acceleration of the solar wind.
Stability of axisymmetric modes in plasma–vacuum equilibria
Authors: LORTZ D.
Published: July 2002

A stability criterion for axisymmetric modes of ideal MHD equilibria
without

wall stabilization is derived for linear profiles with vanishing current
density at

the edge. Using perturbation theory, the critical half-axis ratio of the
elliptical

cross-section is computed for finite aspect ratio.
Non-universality of anomalous transport
Authors: ZASLAVSKY G. M.
Published: July 2002

For low-dimensional Hamiltonian systems with chaotic dynamics,
we discuss the
differences in the kinetic description, and the necessity of windowing
of the time and
parameter space, which is imposed by the differences in the phase-space
topology
and by the stickiness of trajectories at island boundaries.
Membrane fluidity on the surface of Hymenolepis diminuta

(Cestoda): immunological implications
Authors: TAYLOR K. , KUSEL J. R. , HOOLE D.
Published: July 2002

Regional differences of Hymenolepis diminuta to immune

lysis have been investigated by monitoring surface membrane

fluidity utilizing fluorescence recovery after photobleaching (FRAP). Although

the surface membrane of the newly

excysted stage was completely immobile the molecular fluidity of

the strobila membrane of 4-day-old parasites was greater

than that associated with the scolex/neck region. Significant

differences (P>0·001) occurred in the mobility of the
strobila

membrane of 4-day-old H. diminuta from 100-worm infections

compared with 7- and 21-day-old parasites and 4-day-old

individuals from 10-worm infections. Exposure to 50% normal rat serum and

1 mg/ml rat C reactive protein decreased

or eliminated membrane fluidity. The significance of membrane mobility
is

discussed with reference to resistance to

complement-mediated lysis and destrobilation.
Evidence for strategic egg production in a hermaphroditic cestode
Authors: WEDEKIND C. , STRAHM D. , SCHÄRER L.
Published: July 2002

The cestode Schistocephalus solidus is a simultaneous

hermaphrodite that grows in 2 intermediate hosts and reproduces
rapidly within a few days in the gut of a bird. Reproduction takes place

by self- or cross-fertilization. Here, it was tested
whether egg production differs between S. solidus that
reproduce alone and those that are allowed to reproduce in pairs.
Egg production in an in vitro system was found to depend
on the cestodes' social situation. When kept alone, larger
cestodes produced larger eggs. This was not so when kept in pairs
– the difference between these 2 reproductive modes
being highly significant in this respect. Further experiments revealed

that, within the first 3 days, these hermaphrodites
produced a larger total egg mass when kept alone than when kept in
pairs. This was also reflected by the energy contents
of the cestodes after this time-span: selfers had used up more energy
than paired worms. Furthermore, S. solidus appeared
to adjust its investment per egg depending on whether the
offspring will be the result of self- or cross-fertilization. Selfers
produced larger numbers of eggs, but these eggs were smaller and
contained even smaller embryos per given egg size than
eggs of potentially outbreeding cestodes. Selfed eggs reached lower
hatching rates. Although this is to be expected from
inbreeding depression it may also be an effect of the reduced maternal

investment per egg. The observed phenotypic
plasticity in the reproduction of S. solidus is discussed within

4 evolutionary frameworks: local mate competition adjusted
for hermaphrodites, the hermaphrodite's dilemma, bet-hedging, and
sib-competition.
Blood digestion in the mosquito, Anopheles stephensi: the
effects of Plasmodium yoelii nigeriensis on midgut enzyme
activities
Authors: JAHAN N. , DOCHERTY P. T. , BILLINGSLEY P. F. , HURD H.
Published: July 2002

Midgut proteases contribute to the success or failure of Plasmodium infection of the mosquito. This paper examines the
reciprocal effect of Plasmodium yoelii nigeriensis on midgut trypsin, chymotrypsin, aminopeptidase and carboxypeptidase
in the mosquito Anopheles stephensi. The total protein ingested and the rate of protein digestion were unaffected by the
parasite, but more protein was ingested at the first than the second bloodmeal. All peptidases were unaffected by the
presence of the parasite during the first gonotrophic cycle, when ookinetes were penetrating the midgut. In the second
gonotrophic cycle, trypsin and chymotrypsin were unaffected by growing oocysts, but aminopeptidase activity was reduced
in the midguts of infected mosquitoes. Chymotrypsin activity was depressed and aminopeptidase activity elevated during
the second gonotrophic cycle. Plasmodium infection has a negligible effect on bloodmeal digestion and does not limit the
availability of the protein for egg production. The significance of changes in aminopeptidase activity when oocysts are
present is discussed.
Social Structures and their Threats to Moral Agency
Authors: MacIntyre Alasdair
Published: July 2002

Imagine first the case of J (who might be anybody, jemand). J used to inhabit a social order, or rather an area within a social order, where socially approved roles were unusually well-defined. Responsibilities were allocated to each such role and each sphere of role-structured activity was clearly demarcated. These allocations and demarcations were embodied in and partly constituted by the expectations that others had learned to have of those who occupied each such role. For those who occupied those roles to disappoint those expectations by failing to discharge their assigned responsibilities was to invite severe disapproval and other sanctions. To refuse to find one's place within the hierarchies of approved roles, or to have been refused a place, because judged unfit for any such role, was to be classified as socially deviant and irresponsible.

The key moral concepts that education had inculcated into J were concepts of duty and responsibility. His fundamental moral beliefs were that each of us owes it to others to perform her or his assigned duties and to discharge her or his assigned responsibilities. A good human being performs those duties, discharges those responsibilities, and does not trespass into areas that are not her or his concern. A philosopher who comes across the likes of J will understand his attitudes as cultural parodies, in part of Plato (conceiving of justice as requiring ‘that each do her or his own work and not meddle with many things’ Republic 433a) and in part of Kant (doing one's duty just because it is one's duty and not for the sake of any further end), authors who had influenced J's school teachers. A sociologist will entertain the suspicion that in certain types of social order it may be only in the form of parodies that some types of concept can continue to find expression. But for the moment let us put this thought on one side and return to J.
A mediational model of quality of life for individuals
with severe mental health problems
Authors: ZISSI A. , BARRY M. M. , COCHRANE R.
Published: July 2002

Background. Despite the increasing importance of quality

of life in the mental health field, the
theoretical conceptualization of the construct remains poorly developed.
A proposed mediational
model of quality of life, which links subjective quality of life with
self-related constructs, is examined
with a group of long-term psychiatric hostel residents. The present
study aims to develop a measure
of quality of life based on the proposed model, to explore the data
and their implications for service
development and finally to conduct a preliminary analysis of the model's
predictions.

Method. A cross-sectional research design was employed.
Quality of life interviews, using a modified
version of Lehman's Quality of Life Interview, were carried out
with 54 psychiatric residents in
Greece. The model's predictions were examined by using a series of
regression analyses.

Results. The results indicate that perceived improvements
in lifestyle, greater autonomy and positive
self-concept are significantly and directly associated with better
quality of life. In contrast, a direct
relationship between objective indicators and subjective quality of life
was not found.

Conclusions. The traditional two-part quality of life
model that includes objective indicators of life
circumstances and subjective indicators is extended to included
the constructs of self-concept and
perceived autonomy. The present extended mediational model of
quality of life for individuals with
long-term mental health problems appears to have important implications
for the planning and
delivery of mental health programmes.
Outcome of the depressed elderly living in the
community in Liverpool: a 5-year follow-up
Authors: SHARMA V. K. , COPELAND J. R. M. , DEWEY M. E. , LOWE D. , DAVIDSON I.
Published: July 2002

Background. Comparatively little is known about the long-term
natural history of depressive
disorders in the elderly living in the community. This is a follow-up of
a subsample of the
Continuing Health in the Community study random sample of the elderly population
living in
Liverpool.

Methods. The investigators followed up 120 cases of depression
identified by a semi-structured
interview schedule (GMS) for a period of 5 years. A similar number of other
subjects defined as
subcases of depression, other cases of mental illness and a random selection
of non-cases were also
included.

Results. The 5-year outcome for the cases of depression was
worse than the outcome of the non-cases
(relative mortality risk of 2·1, 95% confidence interval 1·1
to 3·9). Thirty-four per cent of the
cases of depression died and 28% had dropped out during the follow-up.
Of the 46 cases of
depression who had a complete follow-up, 22% recovered from their symptoms,
30% were found
to be AGECAT cases at one of the three follow-up waves, 24% were AGECAT
cases at two of the
three follow-up waves and the remaining 24% were AGECAT cases at each follow-up
wave. Fifteen
per cent of the surviving cases of depression were organic cases at the
follow-up. Their anxiety co-morbid state and depression score were identified
as predictors of poor outcome.

Conclusion. The findings of this study indicate that depressive
disorders (most of which were
untreated) found in the elderly community have a poor prognosis.
The unhealthy lifestyle of people with schizophrenia
Authors: BROWN S. , BIRTWISTLE J. , ROE L. , THOMPSON C.
Published: July 2002

Background. Schizophrenia has a high natural mortality of a largely environmental aetiology.
There is, however, little research about possible risk factors. This study measured the diet, cigarette
and alcohol use, exercise and obesity of a cohort of people with schizophrenia and compared results
to general population rates.

Methods. Semi-structured interview using validated research instruments on 102 middle-aged
subjects with a diagnosis of schizophrenia, living in the community. Results were compared to
general population norms using standard statistical tests.

Results. The subjects ate a diet higher in fat and lower in fibre than the general population. They
took little exercise but were not significantly more obese. They smoked heavily but drank less
alcohol. Most differences remained significant after controlling for social class.

Conclusions. People with schizophrenia have an unhealthy lifestyle, which probably contributes to
the excess mortality of the disease. They are therefore an appropriate target group for health
promotion interventions.
Outcome of women admitted to hospital for depressive illness: factors in the prognosis of severe depression
Authors: SHERRINGTON J. M. , HAWTON K. , FAGG J. , ANDREW B. , SMITH D.
Published: July 2002

Background. A previous study of women 9 months after discharge from in-patient treatment for
depression found that low self-esteem as measured by a self-report questionnaire at admission was
associated with a worse prognosis. This study investigates the womens' outcome more than 4 years
after discharge and the continued prognostic relevance of self-esteem and other variables.

Method. Fifty-six women who had been admitted to hospital with major depression and studied in
detail during their admission and 9 months following discharge were traced 4–5 years later. Possible
prognostic factors were investigated in relation to time to recovery and recurrence, and to a global
outcome measure.

Results. In keeping with other published work only 16 out of 52 (31%) women had recovered and
remained well. Fifteen out of 52 (29%) subjects had experienced depressive symptoms for more
than 70% of the follow-up time or died from unnatural causes. Low self-esteem scores recorded at
the initial admission correlated with slow recovery but not subsequent recurrence of depression. The
occurrence of one or more life events in the year preceding admission was associated with a better
prognosis.

Conclusions. The poor long-term prognosis of many women with severe depression was confirmed.
Social factors, such as social support and marital relationships were less important for prognosis
than in previous studies of less severely ill subjects. The prognostic value of self-esteem warrants
further investigation and appears to have therapeutic implications.
Implications of impulsive and affective symptoms for serotonin function in bulimia nervosa
Authors: STEIGER H. , YOUNG S. N. , NG YING KIN N. M. K. , KOERNER N. , ISRAEL M. , LAGEIX P. , PARIS J.
Published: July 2002

Background. Bulimic, impulsive and depressive syndromes have all been associated with
abnormalities in brain serotonin (5-hydroxytryptamine; 5-HT) mechanisms.

Methods. We had 26 bulimic women and 22 normal-eater women report impulsive, affective, self-destructive
and bulimic symptoms, and then provide serial blood samples for measurement of: [3H]-paroxetine
binding in platelets; and, prolactin (PRL) responses following oral meta-chlorophenyl-piperazine (m-CPP).

Results. Bulimic status was associated with markedly reduced density of paroxetine-binding sites,
modest blunting of m-CPP stimulated PRL response, and greater nausea following m-CPP.
Biological variables did not co-vary with most psychopathological or eating-symptom indices.
However, there were inverse associations (in bulimic women only) between scores indicating
impulsivity (largely ‘unreflectiveness’) and density of platelet 5-HT uptake sites.

Conclusions. Our observations link bulimia nervosa to altered 5-HT functioning, and suggest that
there may be a relatively symptom-specific association between impulsivity and reduced 5-HT
reuptake.
Implementing Adult Protection Policies in Kent and East Sussex
Authors: BROWN HILARY , STEIN JUNE
Published: July 2002

This paper reports the extent and nature of adult protection cases
dealt with
by two Social Services Departments during a twelve month period in 1995–6,

within the framework of newly revised generic policies on abuse of vulnerable

adults. The two counties varied in the level of reporting documented and

in the number of cases logged for individuals who fall within the main
four
groups of ‘vulnerable adults’ covered by the policies. Arguments
for consistent
reporting are set out and the tension which exists between formal and
informal approaches to the subsequent investigation of abuse discussed
with
reference to American vulnerable adult statutes. Adult protection work

inevitably overlaps with existing planning and regulation systems such
as
social care assessment, care planning, the care programme approach and

inspection and registration of residential homes. The point at which these

systems need to be augmented by specific adult protection procedures is
a
matter of professional judgement and negotiation within and between agencies.

Continued monitoring of cases reported under the procedures will allow

these authorities to reflect on progress to date and may provide one set
of
norms against which other authorities can evaluate their own practice.
Joel C. Kuipers, Language, identity, and marginality
in Indonesia: The changing nature of ritual speech on the island of
Sumba. (Studies in the social and cultural foundations of language,
18.) Cambridge & New York: Cambridge University Press, 1998. Pp.
xvi, 183. Hb $59.95, pb $19.95.
Authors: Parmentier Richard J.
Published: July 2002

Kuipers' book is based on ethnographic fieldwork
carried out in the Weyewa Highlands of western Sumba, an
island in eastern Indonesia. His initial fieldwork in 1978
resulted in his work Power in performance (1990),
about Weyewa “ritual speech” (tenda)
– a set of political, religious, and personal verbal
genres utilizing a large stock of traditional couplets,
in which the two lines are parallel in both rhythm and
meaning. Returning to the field in 1989, 1990, and 1994,
Kuipers discovered that the obvious loci of change –
new schools, roads, economic activities, and religious
ideas – could not by themselves account for the direction
of change in Weyewa language practices. Stimulated by a
recent body of literature in linguistic anthropology dealing
with “linguistic ideology,” Kuipers attempts
in the present volume to show that changes in ritual speech
genres – reinterpretations, erasures, refunctionalizations,
and condensations – cannot be explained without taking
into account local and imported beliefs about the nature
of language.