bluuebunny/crossref_metadata_2025 huggingface dataset:
Near-critical reflection of internal waves
Authors: DAUXOIS THIERRY , YOUNG W. R.
Published: July 2002

Using a matched asymptotic expansion we analyse the two-dimensional, near-critical
reflection of a weakly nonlinear internal gravity wave from a sloping boundary in
a uniformly stratified fluid. Taking a distinguished limit in which the amplitude
of the incident wave, the dissipation, and the departure from criticality are all
small, we obtain a reduced description of the dynamics. This simplification shows
how either dissipation or transience heals the singularity which is presented by the
solution of Phillips (1966) in the precisely critical case. In the inviscid critical case, an
explicit solution of the initial value problem shows that the buoyancy perturbation
and the alongslope velocity both grow linearly with time, while the scale of the
reflected disturbance is reduced as 1/t. During the course of this scale reduction, the
stratification is ‘overturned’ and the Miles–Howard condition for stratified shear flow
stability is violated. However, for all slope angles, the ‘overturning’ occurs before the
Miles–Howard stability condition is violated and so we argue that the first instability
is convective.

Solutions of the simplified dynamics resemble certain experimental visualizations
of the reflection process. In particular, the buoyancy field computed from the analytic
solution is in good agreement with visualizations reported by Thorpe & Haines
(1987).

One curious aspect of the weakly nonlinear theory is that the final reduced description
is a linear equation (at the solvability order in the expansion all of the
apparently resonant nonlinear contributions cancel amongst themselves). However,
the reconstructed fields do contain nonlinearly driven second harmonics which are
responsible for an important symmetry breaking in which alternate vortices differ in
strength and size from their immediate neighbours.
Thin-film and curtain flows on the outside of a
rotating horizontal cylinder
Authors: DUFFY B. R. , WILSON S. K.
Published: July 2002

We use the lubrication approximation to investigate the steady two-dimensional flow
of a thin film of viscous fluid on the outside of a rigid circular cylinder that is rotating
about its (horizontal) axis. Primarily we are concerned with the flow that ensues when
fluid is supplied continuously as a ‘curtain’ from above the cylinder, so that it flows
round the cylinder and eventually falls off near the bottom. This problem may be thought of as
a ‘hybrid’ of the two classical problems studied by Nusselt (1916a, b)
and Moffatt (1977), concerning, respectively, flow on a stationary cylinder with a
prescribed supply flux, and flow on a rotating cylinder when the supply flux is zero.
For all these problems there are indeterminacies in the steady lubrication solution;
we present a variety of possible solutions, including both
‘full-film’ and ‘partial-film’
solutions, and solutions that involve smooth ‘jumps’ in the free-surface profile. We
show, for example, that stagnation points can occur in the flow, that solutions exist
that do not have top-to-bottom symmetry, that in curtain flows the curtain generally
takes a characteristic ‘buckled’ shape, and that in
full-film curtain flows there is always
some fluid that is ‘trapped’ near the rotating cylinder, never escaping as part of the
curtain that detaches at the bottom of the cylinder. Also we show that finite-thickness
films involving jumps cannot occur in these coating flows (though they are known to
occur in rimming flows).
Numerical studies of transonic BZT gas flows around thin airfoils
Authors: WANG CHUN-WEI , RUSAK ZVI
Published: July 2002

Numerical studies of two-dimensional, transonic flows of dense gases of retrograde
type, known as BZT gases, around thin airfoils are presented. The computations are
guided by a recent asymptotic theory of Rusak & Wang (1997). It provides a uniformly
valid solution of the flow around the entire airfoil surface which is composed of outer
and inner solutions. A new transonic small-disturbance (TSD) equation solver is
developed to compute the nonlinear BZT gas flow in the outer region around most
of the airfoil. The flow in the inner region near the nose of the airfoil is computed
by solving the problem of a sonic flow around a parabola. Numerical results of the
composite solutions calculated from the asymptotic formula are compared with the
solutions of the Euler equations. The comparison demonstrates that, in the leading
order, the TSD solutions of BZT gas flows represent the essence of the flow character
around the airfoil as computed from the Euler equations. Furthermore, guided by the
asymptotic formula, the computational results demonstrate the similarity rules for
transonic flows of BZT gases. There are differences between the self-similar cases that
may be related to the error associated with the accuracy of the asymptotic solution.
A discussion on the flow patterns around an airfoil at transonic speeds and at various
upstream thermodynamic conditions is also presented. The paper provides important
guidelines for future studies on this subject.
Dissipation-range geometry and scalar spectra in
sheared stratified turbulence
Authors: SMYTH WILLIAM D.
Published: July 2002

Direct numerical simulations of turbulence resulting from Kelvin–Helmholtz
instability in stratified shear flow are used to examine the geometry of the dissipation
range in a variety of flow regimes. As the buoyancy and shear Reynolds numbers that
quantify the degree of isotropy in the dissipation range increase, alignment statistics
evolve from those characteristic of parallel shear flow to those found previously in
studies of stationary, isotropic, homogeneous turbulence (e.g. Ashurst et al. 1987;
She et al. 1991; Tsinober et al. 1992). The analysis yields a limiting value for the
mean compression rate of scalar gradients that is expected to be characteristic of all
turbulent flows at sufficiently high Reynolds number.

My main focus is the value of the constant q that appears in both the Batchelor
(1959) and Kraichnan (1968) theoretical forms for the passive scalar spectrum. Taking
account of the effects of time-dependent strain, I propose a revised estimate of q,
denoted qe, which appears to agree with spectral shapes derived from simulations
and observations better than do previous theoretical estimates. The revised estimate
is qe = 7.3±4, and is expected to be valid whenever the buoyancy Reynolds number
exceeds O(102). The Kraichnan (1968) spectral form, in which effects of intermittency
are accounted for, provides a better fit to the DNS results than does the Batchelor
(1959) form.
Application of the Ffowcs Williams/Hawkings
equation to two-dimensional problems
Authors: GUO Y. P.
Published: July 2002

This paper discusses the application of the Ffowcs Williams/Hawkings equation to
two-dimensional problems. A two-dimensional version of this equation is derived,
which not only provides a very efficient way for numerical implementation, but also
reveals explicitly the features of the source mechanisms and the characteristics of the
far-field noise associated with two-dimensional problems. It is shown that the sources
can be interpreted, similarly to those in three-dimensional spaces, as quadrupoles
from turbulent flows, dipoles due to surface pressure fluctuations on the bodies in the
flow and monopoles from non-vanishing normal accelerations of the body surfaces.
The cylindrical spreading of the two-dimensional waves and their far-field directivity
become apparent in this new version. It also explicitly brings out the functional
dependence of the radiated sound on parameters such as the flow Mach number and
the Doppler factor due to source motions. This dependence is shown to be quite
different from those in three-dimensional problems. The two-dimensional version is
numerically very efficient because the domains of the integration are reduced by
one from the three-dimensional version. The quadrupole integrals are now in a
planar domain and the dipole and monopole integrals are along the contours of the
two-dimensional bodies. The calculations of the retarded-time interpolation of the
integrands, a time-consuming but necessary step in the three-dimensional version, are
completely avoided by making use of fast Fourier transform. To demonstrate the
application of this, a vortex/airfoil interaction problem is discussed, which has many
practical applications and involves important issues such as vortex shedding from the
trailing edge.
Linear stability of free shear flows of fibre suspensions
Authors: AZAIEZ J.
Published: July 2002

A linear stability analysis of the mixing layer in the presence of fibre additives is
presented. Using a formulation based on moments of the probability distribution function
to determine the particle orientation, we extend the classical linear stability theory
and derive a modified Orr–Sommerfeld equation. It is found that, for large Reynolds
numbers, the flow instability is governed by two parameters: a dimensionless group
H, analogous to a reciprocal Reynolds number representing the importance of inertial
forces versus viscous forces associated with the anisotropic elongational viscosity of
the suspension; and a coefficient CI that accounts for inter-particle hydrodynamic interactions.
A parametric study reveals that both parameters can induce an important
attenuation of the flow instability. Furthermore, we show that the stabilizing effects
arise from the orientation diffusion due to hydrodynamic interactions, and not from
the anisotropy induced by the presence of fibres in the flow, as speculated before.
The examination of profile contours of different perturbation terms and the analysis
of the rate of production of enstrophy show clearly that the main factor behind the
reduction of the flow instability is associated with the fibre shear stress disturbance.
This disturbance acts as a dissipative term as the fibres, due to the orientational
diffusivity arising from hydrodynamic interactions, deviate from the fully aligned
anisotropic orientation. On the other hand, fibre normal stresses act as a destabilizing
factor and are important only in the absence of hydrodynamic interactions.
Quasi-periodicity in the wake of a rotationally oscillating cylinder
Authors: BAEK SEUNG-JIN , SUNG HYUNG JIN
Published: July 2002

A systematic numerical analysis is performed for the quasi-periodicity in the wake
where a circular cylinder is rotationally oscillated in time. The main emphasis is placed
on the identification of frequency selection subjected to the controlled perturbations
in the vicinity of lock-on. The frequency responses are scrutinized by measuring the
lift coefficient (CL). A direct numerical simulation is made to portray the unsteady
dynamics of wake flows at Re = 110. It is found that, after the shedding frequency
is bifurcated at the boundary of lock-on, one frequency follows the forcing frequency
and the other gradually converges to the natural shedding frequency. The asymptotic
convergence phenomena are observed by solving the Van der Pol equation and the
circle map. A new frequency selection formula is proposed. The quasi-periodic states
are interpreted in terms of the forcing frequency, shedding frequency and modulated
frequencies by employing the torus concept and the CL(t) diagram. In the quasi-periodic state, the variation of magnitudes and relevant phase changes of CL with
forcing phase are examined.
Haiti: International Force or National Compromise?
Authors: MARTIN IAN
Published: July 2002

The objective is clear: to reinstate the legitimate President in his
functions and ensure his maintenance in power until the end of his mandate. The
question which is posed is to know how to achieve this objective: international
force or national compromise? – Boutros Boutros-Ghali, UN Secretary-General.
The role of non-violent action in
the downfall of apartheid
Authors: Zunes Stephen
Published: July 2002

Against enormous odds, non-violent action proved to be a major
factor
in the downfall of apartheid in South Africa, and the establishment of
a
democratic black majority government, despite predictions that the transition

could come only through a violent revolutionary cataclysm. This was largely

the result of conditions working against a successful armed overthrow of
the
system, combined with the ability of the anti-apartheid opposition to take

advantage of the system's economic dependence on a cooperative black
labour
force. This article traces the history of nonviolent resistance to apartheid,
its
initial failures, and the return in the 1980s to a largely non-violent
strategy
which, together with international sanctions, forced the government to

negotiate a peaceful transfer to majority rule.
On the inadmissibility of non-evolutionary shocks
Authors: FALLE S. A. E. G. , KOMISSAROV S. S.
Published: July 2002

In recent years, numerical solutions of the equations of compressible magnetohydrodynamic
(MHD) flows have been found to contain intermediate shocks
for certain kinds of problems. Since these results would seem to be in conflict with
the classical theory of MHD shocks, they have stimulated attempts to reexamine
various aspects of this theory, in particular the role of dissipation. In this paper,
we study the general relationship between the evolutionary conditions for discontinuous
solutions of the dissipation-free system and the existence and uniqueness
of steady dissipative shock structures for systems of quasilinear conservation laws
with a concave entropy function. Our results confirm the classical theory. We also
show that the appearance of intermediate shocks in numerical simulations can be
understood in terms of the properties of the equations of planar MHD, for which
some of these shocks turn out to be evolutionary. Finally, we discuss ways in which
numerical schemes can be modified in order to avoid the appearance of intermediate
shocks in simulations with such symmetry.
Transonic magnetohydrodynamic flows
Authors: LIFSCHITZ A. , GOEDBLOED J. P.
Published: July 2002

Stationary flows of an ideal plasma with
translational symmetry along the (vertical) z axis
are considered, and it is demonstrated how they can be described in
the intrinsic (natural) coordinates (ξ, η, &), where ξ is a label
of
flux and stream
surfaces, η is the total pressure and ϑ is the angle between
the horizontal magnetic
(and velocity) field and the x axis. Three scalar nonlinear
equilibrium equations
of mixed elliptic–hyperbolic type for ϑ(ξ, η),
ξ(η, ϑ) and η(ϑ, ξ) respectively are derived.
The equilibrium equation for ϑ(ξ, η) is especially useful,
and has considerable
advantages compared with the coupled system of algebraic–differential
equations
that are conventionally used for studying plasma flows. In particular,
for this equation the location of the regions of ellipticity and
hyperbolicity can be determined
a priori. Relations between the equilibrium equation for ϑ(ξ,
η)
and the nonlinear hodograph equation for ξ(η, ϑ) are
elucidated. Symmetry
properties of the intrinsic equilibrium equations are discussed in detail
and their self-similar solutions are
described. In particular, magnetohydrodynamic counterparts of several classical
flows of an ideal fluid (the Prandtl–Meyer flows
around a corner, the spiral flows
and the Ringleb flows around a plate, etc.) are found. Stationary flows
described in
this paper can be used for studying both astrophysical and thermonuclear
plasmas.
New observations on Loxosomella tonsoria, with notes on distribution and host specificity of the genus
Authors: Arroyo N.L. , Benito J.
Published: July 2002

Loxosomella tonsoria (Entoprocta: Loxosomatidae) was found associated with the polynoid polychaete Lepidonotus clava collected among the algae and debris scraped from the intertidal level at the rocky shore of Limens (Pontevedra, Spain). New features are added to the original description, together with the first description of its buds. Host specificity of the genus and distribution of this species are discussed.
First record of the giant squid Architeuthis sp. (Architeuthidae) in the Mediterranean Sea
Authors: González María , Fernández-Casado Manuel , Rodríguez Ma. del Pilar , Segura Antonio , Martín Juan Jesús
Published: July 2002

The stranding of a female specimen of the genus Architeuthis, a species not previously recorded in the Mediterranean Sea, is reported from the southern Spanish coast (Alboran Sea, western Mediterranean). The geographical distribution of the species is discussed.
On Mediterranean and some north-eastern Atlantic Liparidae (Pisces: Scorpaeniformes) with the restoration of Eutelichthys
Authors: Matallanas J.
Published: July 2002

The hyoid arch and branchiostegal rays of Paraliparis leptochirus (Pisces: Liparidae) and of Paraliparis murieli are described for the first time. The restoration of the validity of Eutelichthys Tortonese on the basis of the presence of only five branchiostegal rays in P. leptochirus, its type species, is proposed. Paraliparis murieli has, as the other Paraliparis spp., a hyoid arch with six branchiostegal rays. The endochondral pectoral girdle of P. leptochirus, P. murieli and P. hystrix is described for the first time, and some data about the girdle of P. edwardsi are given. Differences between P. hystrix and P. murieli, described simultaneously, and between P. murieli and P. australis are established.
Effect of habitat complexity and predatory style on the capture success of fish feeding on aggregated prey
Authors: Flynn A.J. , Ritz D.A.
Published: July 2002

When offered a choice between open water and a ‘vegetated’ area of an aquarium (artificial sea grass), mysid (Paramesopodopsis rufa) swarms always selected open water. In contrast, juvenile and adult sea horses, Hippocampus abdominalis, which feed by ambush predation, always selected vegetated areas even when their mysid prey occurred in the adjacent clear water. Lunging predators, Australian salmon (Arripis trutta), always preferred open water to vegetated regions of the tank. Increasing vegetation density, i.e. from low to medium habitat complexity had a positive effect on capture success of juvenile and adult sea horses feeding on mysid swarms. However, number of attacks by juvenile sea horses, but not adults, was significantly reduced in higher density vegetation. Number of attacks by Australian salmon decreased as vegetation density increased but capture success, nonetheless, increased. Density of vegetation did not significantly affect the number of unsuccessful attacks by adult sea horses. Whereas proportion of unsuccessful attacks increased with vegetation density for juvenile sea horses, it decreased for juvenile salmon. This result is thought to be due to the fact that high vegetation densities disrupt structure of the prey swarm, itself a defensive formation, leaving a large number of more vulnerable small groups. Cohesive escape responses of a large swarm are likely to be a more effective defence against a lunging predator than against an ambush predator whose strategy is to use stealth to avoid provoking escape responses. Dense vegetation will militate against this strategy.
Assessment of errors in cetacean diet analysis: in vitro digestion of otoliths
Authors: Wijnsma G. , Pierce G.J. , Santos M.B.
Published: July 2002

Research into the feeding habits of cetaceans has traditionally relied on examining samples taken from the digestive tracts of commercially caught or stranded and by-caught animals. This depends on the identification and measurement of hard parts such as fish otoliths. Otoliths are often partially digested in the stomach, making quantitative estimates of fish size from otolith size biased.

As a preliminary attempt to quantify the size reduction of otoliths found in the stomachs of small cetaceans, an in vitro digestion experiment was carried out. Otoliths of herring, whiting, poor cod and haddock were digested at 37°C, pH=3·6, and measured every 60 min.

Linear regressions relating otolith size to digestion time and original size generally provided an adequate description of the time course of size reduction. The parameter that changed most rapidly due to digestion was otolith thickness. Differences in digestion rates between species reflect the general robustness and shape of the otoliths.

A simulation using actual dietary data showed that the overall diet composition was not radically changed by accounting for otolith digestion, although the apparent contribution of herring increased as the assumed digestion time is increased, because herring otoliths were the most susceptible to digestion.
New host records for Haemogregarina bigemina from the coast of southern Africa
Authors: Smit N.J. , Davies A.J.
Published: July 2002

One hundred and fifty intertidal fishes were captured at Jeffreys Bay in July 1996 and February 1997, and at De Hoop Nature Reserve in April 1997, South Africa. Caffrogobius caffer, Chorisochismus dentex, Clinus superciliosus, and Clinus cottoides were all parasitised by haematophagous larvae of the isopod, Gnathia africana, and between 22 and 81% of fishes were infested with 1 to 76 larvae each. Of those fishes examined for blood parasites, 35/46 (76.1%) had an intraerythrocytic haemogregarine identified as Haemogregarina (sensu lato) bigemina, but only Clinus superciliosus and Clinus cottoides were infected. Gamonts of the haemogregarine, some undergoing syzygy, were also present in 50% of stained batches of the anterior hindgut contents of G. africana larvae which had fed on Clinus superciliosus, but were absent from larvae taken from Clinus cottoides and Chorisochismus dentex. This study provides new host records for H. bigemina and further evidence that gnathiid isopods play a role in the transmission of the haemogregarine.
Automatic recording of the radular activity of dogwhelks (Nucella lapillus) drilling mussels (Mytilus edulis)
Authors: Rovero F. , Hughes R. N. , Chelazzi G.
Published: July 2002

The radular activity of dogwhelks, Nucella lapillus, drilling mussels, Mytilus edulis, was monitored by piezoelectric transducers and recorded by an automatic digital system. In this way, for the first time, the drilling behaviour of dogwhelks was analysed in detail. Radular activity was similar to that previously recorded for limpets, each radular stroke (rasp) being formed by a sequence of 1–8 unit events, each probably corresponding to the application of one row of radular teeth on the substratum. During drilling, radular rasping followed a consistent pattern, each bout of radular rasping (lasting about 6–8 min) being followed by a period of radular inactivity (lasting about 35 min), when chemical dissolution is probably applied. The periodicity with which rasping was applied decreased during the drilling sequence (from about 25 min in the first quarter of the drilling process to about 40 min in the last quarter), together with a decrease in the rasping rate, i.e. number of radular rasps per min (from about 12 to about five rasps per min). Accordingly, the total number of radular rasps recorded during the first quarter of the drilling time was higher than during the other quarters (from about 3000 to about 500 rasps). The role of the radula in shell penetration was therefore rather extensive, accounting, during the first quarter of the process, for about 34% of drilling time. The results are discussed in relation to studies of chemical dissolution and mussel shell ultrastructure.
The Effect of Government Policy and Institutions on Chinese Overseas Acculturation: The Case of Malaysia
Authors: FREEDMAN AMY L.
Published: July 2002

This work looks at how Malaysia's political institutions and policies have constrained Chinese acculturation with the
dominant Malay population. Particular attention is paid to the nature of electoral institutions; such as the ethnic party
structure, the apportionment of electoral districts, and the debate over Malaysia's education system. These political
institutions, and not just the coercive apparatus of the state, coupled with the way the Constitution defines a person as
‘Malay’, effectively maintain a distinct boundary between who is Malay and who is Chinese or Indian. Ethnic
categorization in Malaysia has, in the past, masked equally wide divisions between classes. More recent efforts at creating a
‘Malaysian’ national identity may clash with a political structure still largely organized by ethnicity, and may bring
these other fissures to the forefront.
Habituating the great apes: the disease risks
Authors: Woodford Michael H. , Butynski Thomas M. , Karesh William B.
Published: July 2002

All six great apes, gorillas Gorilla gorilla and G. beringei, chimpanzees Pan troglodytes and P. paniscus, and orang-utans Pongo pygmaeus and P. abelii, are categorized as Endangered on the 2000 IUCN Red List and face many threats to their continued existence in the wild. These threats include loss of habitat to settlement, logging and agriculture, illegal hunting for bushmeat and traditional medicine, the live ape trade, civil unrest and infectious diseases. The great apes are highly susceptible to many human diseases, some of which can be fatal while others can cause marked morbidity. There is increasing evidence that diseases can be transmitted from humans to free-living habituated apes, sometimes with serious consequences. If protective measures are not improved, ape populations that are frequently in close contact with people will eventually be affected by the inadvertent transmission of human diseases. This paper describes the risks, sources and circumstances of infectious disease transmission from humans to great apes during and consequent upon habituation for tourism and research. A major problem is that the regulations that protect habituated apes from the transmission of disease from people are often poorly enforced. Suggestions are made for improving the enforcement of existing regulations governing ape-based tourism, and for minimizing the risk of disease transmission between humans, both local people and international visitors, and the great apes.
Cloning, heterologous expression and antigenicity of a
schistosome cercarial protease
Authors: PRICE H. P. , DOENHOFF M. J. , SAYERS J. R.
Published: July 2002

A gene coding for the 30 kDa Schistosoma mansoni cercarial
protease was amplified using the polymerase chain reaction
(PCR) from genomic DNA templates. Cloning and sequencing of several independent
PCR clones revealed the presence
of an intron additional to the one described in the original cloning of
the
gene. The 3 exons were cloned into expression
vectors so that they could be expressed as separate glutathione-S-transferase
(GST) translational fusions. Recombinant
bacteria carrying these expression plasmids expressed the fusion proteins
at
high levels. Western blotting of bacterial
lysates with sera raised against the native S. mansoni cercarial
protease showed that all 3 exons were recognized. Thus we
have produced recombinant bacteria capable of providing large amounts of
an
S. mansoni antigen for immunological
studies and evaluation as a candidate vaccine.
Reduced genetic variability within coding and non-coding
regions of the Echinococcus multilocularis genome
Authors: HAAG K. L. , ZAHA A. , ARAÚJO A. M. , GOTTSTEIN B.
Published: July 2002

Echinococcus multilocularis, a vulpine intestinal tapeworm,
is the causative agent of alveolar echinococosis in humans, one
of the most severe and lethal parasitic infections in man. To date, there
is
very little knowledge about the genetical
polymorphism of this parasite. To assess sequence polymorphism, we analysed
a
sample of 33 E. multilocularis isolates
from Europe, North America and Asia by PCR-SSCP followed by nucleotide
sequencing. This assessment was performed
comparatively to sheep, cattle and pig E. granulosus strains.
Coding
(nuclear antigen B and mitochondrial NADH
dehydrogenase genes) and non-coding (introns of actin and homeobox-containing
genes)
regions of the parasite genome
were chosen as targets. Since the estimated nucleotide diversity among
genotypes
of E. multilocularis were, in general, 10
times lower than among the recognized different strains of E. granulosus,
we suggest that the conventional classification
of the former species in 2 separated strains (European and North
American) should be reviewed.
Parasite immune evasion and exploitation: reflections and projections
Authors: DAMIAN R. T.
Published: July 2002

Recent developments in parasite immune evasion and exploitation
are
reviewed with special reference to the papers
presented in this volume. Parasites, broadly defined, of animals with good

immune responses have evolved many strategies
that adapt them to survive and reproduce. These strategies may be passive,

or may involve active intervention with host
immune regulation, and can be categorized as immune evasion, immune exploitation

and molecular piracy. The concept
of immune evasion began with Paul Ehrlich's demonstration of antigenic

variation in African trypanosomes and was
reinforced by later ideas on molecular mimicry. Molecular mimicry is updated

in the light of recent discoveries about
degeneracy and plasticity of TCR/MHC-peptide recognition. Possible

connections between two of its postulated consequences, evasion and autoimmunity,

are discussed. Another putative consequence of molecular mimicry, host
antigenic
polymorphism, is also updated. The concept of exploitation of host immune

responses by parasites has been reinforced
by new data on its first known examples, especially the immune dependence
of
schistosome egg excretion. Newer examples
include use of host cytokines as parasite growth factors, virokines,
viroreceptors and helminth pseudocytokines. Finally,
questions of host gene capture by viruses and possible horizontal gene
transfer
between host and parasite mediated by
retroviruses are examined. The latter is compared with molecular conservation

as a source of molecular mimicry and other aspects of host–parasite
coevolution.
Environmental effects on transmission of Discocotyle
sagittata (Monogenea): egg production and development
Authors: GANNICOTT A. M. , TINSLEY R. C.
Published: July 2002

Egg production by the freshwater gill monogenean Discocotyle
sagittata infecting rainbow trout (Oncorhynchus mykiss) was

monitored at 5, 13 and 18°C; eggs were incubated at 6, 10, 13, 15,
16, 18, 22 and 26°C and the hatching times determined.
Mean per capita output at 13°C ranged from 0·8 eggs/worm/day
(e/w/d) to 18·3 e/w/d for 25 hosts (burdens 1–17

worms/host). Average egg production rates for worms in single burdens
varied from 3 e/d to 14·6 e/d at 13°C, mean
7·6 e/d (±0·63) (n=8). Egg production
was temperature dependent, increasing from a mean of 1·5 e/w/d
at 5°C to 12·0
e/w/d at 18°C. Developmental rate was also temperature dependent:
larvae began hatching after 84 days at 6°C, 28 days
at 13°C, and 20 days at 18°C. Eggs laid within the same 24 h period
hatched over 3–7 days at 13–18°C; this range was
extended at decreasing temperatures. Egg viability was generally high:
between 13 and 18°C a mean of 92% of larvae
successfully emerged. However, viability declined at the highest and lowest
temperatures (23% hatching at 6°C, 55%
at 8°C and 47% at 26°C). The implications for seasonal parasite
transmission are discussed.
Incidence from coincidence: patterns of tick infestations
on rodents facilitate transmission of tick-borne encephalitis
virus
Authors: RANDOLPH S. E. , MIKLISOVÁ D. , LYSY J. , ROGERS D. J. , LABUDA M.
Published: July 2002

Tick-borne encephalitis (TBE) virus has a highly focal distribution
through Eurasia. Endemic cycles appear to depend
on the transmission of non-systemic infections between ticks co-feeding
on the same rodent hosts. The particular features
of seasonal dynamics and infestation patterns of larval and nymphal Ixodes
ricinus, but not Dermacentor reticulatus, from
4 regions within TBE foci in Slovakia, are such as to promote TBE virus
transmission. The distributions of larvae and
nymphs on their principal rodent hosts are highly aggregated and, rather
than being independent, the distributions of each
stage are coincident so that the same ca. 20% of hosts feed about
three-quarters of both larvae and nymphs. This results
in twice the number of infectible larvae feeding alongside potentially
infected nymphs compared with the null hypothesis
of independent distributions. Overall, co-feeding transmission under these
circumstances brings the reproductive number
(R0) for TBE virus to a level that accounts quantitatively
for maintained endemic cycles. Essential for coincident aggregated
distributions of larvae and nymphs is their synchronous seasonal activity.
Preliminary comparisons support the prediction
of a greater degree of coincident seasonality within recorded TBE foci
than outside. This identifies the particular climatic
factors that permit such patterns of tick seasonal dynamics as the primary
predictors for the focal distribution of TBE.
Molecular karyotype diversity in the microsporidian
Encephalitozoon cuniculi
Authors: BIDERRE C. , MATHIS A. , DEPLAZES P. , WEBER R. , METENIER G. , VIVARES C. P.
Published: July 2002

The microsporidian Encephalitozoon cuniculi can infect numerous mammals, including man. Three strains of E. cuniculi
have been identified so far, the major marker being the number of a tetranucleotide repeats in the rDNA internal transcribed spacer. We investigated diversity at the chromosomal level through the electrophoretic karyotypes obtained from 15 E.
cuniculi isolates from 5 different host species. All preparations provided patterns with 9–12 bands within a narrow
molecular size range. Six karyotype forms were distinguished, involving subdivision of strain I into 3 types (A, B, C) and
strain II into 2 types (D, E). The types A, B and C were mainly associated with isolates from rabbits of different
geographical origins. The types D, E and F were characterized by a reduced chromosome size range, 2 of these appearing
specific to a carnivorous host species (D in dog and F in blue fox). Hybridization experiments showed that all E. cuniculi
isolates possess 11 chromosomes, with a size polymorphism entailing occasional electrophoretic comigration of heterologous
chromosomes and differential migration of homologous ones. DNA rearrangements should occur during mitosis
and the hypothesis of diploidy for the basic state of E. cuniculi seems likely.
Small subunit rDNA phylogeny of Bacillidium sp.
(Microspora, Mrazekiidae) infecting oligochaets
Authors: NILSEN F.
Published: July 2002

Small subunit (SSU) rDNA has been sequenced from a microsporidium, identified as a member of the genus Bacillidium
obtained from an oligochaete. The length of the amplified PCR product was 1386 bp which is currently the longest
microsporidium SSU sequence known. Phylogenetic analysis using 28 microsporidia SSU sequences, using 3 different
tree-building methods indicated that Bacillidium sp. may be one of the earliest branches on the microsporidia tree.
However, bootstrapping failed to give a high score (more than 50%) for the position of Bacillidium sp. The branch leading
to Bacillidium sp. was long, indicating that this species is not closely related to any of the other microsporidia so far studied
by means of rDNA.
Host-dependent and seasonal variation in opisthaptoral
hard parts of Gyrodactylus cf. arcuatus from
three Pomatoschistus spp. and G. arcuatus from
Gasterosteus aculeatus: a multivariate approach
Authors: GEETS A. , APPLEBY C. , OLLEVIER F.
Published: July 2002

Gyrodactylus arcuatus-like monogeneans collected from the gills of 3 goby species, Pomatoschistus minutus, P. lozanoi and
P. pictus, from the Voordelta Area (SW Netherlands) were compared on a morphometric basis with G. arcuatus from its
type host, the three-spined stickleback, Gasterosteus aculeatus. Univariate and multivariate analysis was carried out on
measurements of 17 characters of the opisthaptoral hard parts of 268 specimens. The contribution of host-dependent and
seasonal factors to the observed morphological variation are discussed. Univariate statistics (ANOVA) were used to detect
features that were useful in separating the gyrodactylids from the different host groups. Subsequent factor analysis and
discriminant analysis, combining all variables, led to the separation of 3 distinct forms (possibly species) dependent on
the host species harbouring them. G. arcuatus (sensu stricto) was only present on G. aculeatus, while P. minutus and P.
lozanoi carried a common species, Gyrodactylus sp. 1, and P. pictus hosted Gyrodactylus sp. 2. Seasonal variation in size
of the sclerities was demonstrated on the Gyrodactylus species from P. minutus and P. lozanoi, and should be taken into
consideration when specimens are compared. The findings are discussed in view of the possibility of phylogenetic host
specificity of the gyrodactylids occurring on goby species that live sympatrically in the Voordelta area.
Molecular cloning and characterization of gut-derived
cysteine proteinases associated with a host protective
extract from Haemonchus contortus
Authors: SKUCE P. J. , REDMOND D. L. , LIDDELL S. , STEWART E. M. , NEWLANDS G. F. J. , SMITH W. D. , KNOX D. P.
Published: July 2002

Cysteine proteinases have been implicated in the protection conferred by vaccination with detergent-soluble extracts of
Haemonchus contortus. In the present study, antisera from sheep refractory to Haemonchus challenge following vaccination
with a ‘proteinase-enriched’ Haemonchus gut membrane extract, were employed to screen a cDNA expression library of
the adult parasite. This resulted in the isolation of 3 cDNAs (designated hmcp1, 4 and 6) encoding cathepsin B-like
cysteine proteinases. Immunocytochemical studies specifically localized the products of these genes to the microvillar
surface of the parasite's gut and RT–PCR experiments revealed that these were developmentally regulated, being expressed
exclusively during the blood-feeding parasitic stages. In addition, a generic PCR approach was adopted in order to identify
the predominant cysteine proteinases in a UK strain of Haemonchus. A panel of 5 cDNAs, including hmcp1 and 4, was
amplified in this way. Genomic Southern blot analysis indicated that some of these enzymes were encoded by single-copy
genes, whereas others were encoded by multi-copy genes. Subsequent sequence analysis revealed that the proteases
identified in this study were distinct from those previously reported in USA strains of the parasite.
Transmission-blocking immunity to Plasmodium
falciparum in malaria-immune individuals is associated
with antibodies to the gamete surface protein Pfs230
Authors: HEALER J. , McGUINNESS D. , CARTER R. , RILEY E.
Published: July 2002

Malaria-immune human sera were tested for their ability to affect the infectivity of Plasmodium falciparum gametocytes
to Anopheles stephensi mosquitoes. Transmission-reducing effects of the sera were associated with the presence of
antibodies to the gamete surface protein, Pfs230. Enhancement of transmission, manifest as elevated numbers of oocysts
relative to controls, was observed for a number of sera, but was not found to be associated with antibodies against Pfs230.
These results confirm that Pfs230 is a possible candidate for inclusion in a transmission-blocking malaria vaccine.
Accumulation and distribution of lead in the archiacanthocephalan Moniliformis moniliformis from experimentally infected rats
Authors: SURES B. , JÜRGES G. , TARASCHEWSKI H.
Published: July 2002

It recently became clear that adult eo- and palaeacanthocephalans parasitizing fish can bioconcentrate several heavy metals
to significantly higher concentrations than the tissues of their definitive hosts. Following this discovery the lead accumulation
of the archiacanthocephalan Moniliformis moniliformis was investigated using experimentally infected male Wistar
rats of the CD-M-strain. The worms were allowed to grow up for 4 weeks post-infection followed by a 3 weeks oral lead
exposure of the rats. After the exposure period the rats were killed and the metal levels were determined in muscle, liver,
intestine and kidney of the rats as well as in different organs of female and male acanthocephalans. Lead concentrations
were found to be highest in female M. moniliformis followed by the kidneys of the rats. Male worms contained approximately
the same lead concentration as the hosts' kidneys. Lead analysis of the worms' organs revealed the highest lead
concentration in the eggs of female acanthocephalans, followed by the cement gland of male Worms. Whilst the lead
burden of the presoma was higher than that detected in the kidneys of the rats, the lead content of the metasoma was even
lower than in the kidneys. A lead uptake of M. moniliformis from the intestinal lumen of the host became apparent as the
faeces of infected rats contained significantly less lead compared to the uninfected conspecifics. Thus, this study reveals
that lead accumulation also occurs in archiacanthocephalans parasitizing mammals. But the degree of metal bioconcentration
is considerably lower compared to eo- and palaeacanthocephalans in fish. Anyway, due to a lack of adequate
sentinel species in terrestrial biotopes the host–parasite system rat– M. moniliformis appears to be a useful and promising
bioindication system especially in urban ecosystems in temperate regions.
A myxozoan-like parasite causing xenomas in the brain of the mole, Talpa europaea L., 1758 (Vertebrata, Mammalia)
Authors: FRIEDRICH C. , INGOLIC E. , FREITAG B. , KASTBERGER G. , HOHMANN V. , SKOFITSCH G. , NEUMEISTER U. , KEPKA O.
Published: July 2002

Light and transmission electron microscopy revealed pericytes of brain capillaries of moles (Talpa europaea L., 1758) as
parasitized intracellularly. These host cells were enlarged and of globular or ellipsoid shape, and incorporated a cell-within-cell sequence of primary, secondary and, rarely found, tertiary developmental stages of an eukaryotic organism.
Other stages like spores were not discovered either in brain or in other organs. Due to the vertebrate host, and the parasitic
cells showing the enveloped state this parasite can be classified as belonging to the Myxozoa rather than Paramyxea. Since
spores, which would allow an exact identification of the parasite, could not be detected and mammals are very unusual
hosts for Myxozoa, the parasite was designated a myxozoan-like organism.
Philosophy as a Humanistic Discipline
Authors: Williams Bernard
Published: July 2002

Philosophy should not try to assimilate itself to the aims of the sciences. Scientism stems from the false assumption that a representation of the world minimally based on local perspectives is what best serves self-understanding. Philosophy must concern itself with the history of our conceptions, and we must overcome the need to think that this history should ideally be vindicatory. There is no basic conflict between arguing within the framework of our ideas, reflectively making better sense of them, and understanding their highly contingent history. The third of these activities is an inescapable part of the second.
Agents and their Actions
Authors: ALVAREZ MARIA , HYMAN JOHN
Published: July 2002

In the past thirty years or so, the doctrine that actions are events has become an essential, and sometimes unargued, part of the received view in the philosophy of action, despite the efforts of a few philosophers to undermine the consensus. For example, the entry for Agency in a recently published reference guide to the philosophy of mind begins with the following sentence:

A central task in the philosophy of action is that of spelling out the differences between events in general and those events that fall squarely into the category of human action.

There is no consensus about what events are. But it is generally agreed that, whatever events may prove to be, actions are a species or a class of events.
We believe that the received view is mistaken: actions are not events. We concede that for most purposes, the kind of categorial refinement which is involved in either affirming or denying that actions are events is frankly otiose. Our common idiom does not stress the difference between actions and events, at least not in general terms, because it has no need to. Perhaps it sounds a little odd to say that some events are performed; but if we balked at describing, say, the abdication of Edward VIII as one of the politically significant events in Britain in 1936, it could not be for metaphysical reasons. And since actions, like events, are datable — though often, as we shall see, only imprecisely — actions are said to take place and to occur. But an important class of actions consist in moving something; indeed, according to many philosophers, every action consists in moving something. And when we consider actions of this sort from a theoretical point of view it becomes imperative to distinguish between actions and events. Or so we shall argue.
Colour: Physical or Phenomenal?
Authors: WAHL RUSSELL , WESTPHAL JONATHAN
Published: July 2002

We wish to defend Jonathan Westphal's view that colour is complex against a recent ‘phenomenological’ criticism of Eric Rubenstein. There is often thought to be a conflict between two kinds of determinants of colour, physical and phenomenal. On the one hand there are the complex physical facts about colour, such as the determination of a surface colour by an absorption spectrum. There is also, however, the fact that the apparently simple phenomenological quality of what is seen is a function of the physiological and psychological state of the viewing subject. Should the physical trump the phenomenal, or is it the other way round?

Much of the phenomenal variation of colour, however, is explained by physical facts. There is a physics and a psychophysics of colour. Colours appear, to the colour scientists at least, to be in some sense objective, a sense not explained by the view that they are purely phenomenal. Taking physics and psychophysics into account will mean rejecting the claim that the content of what our concepts of colours are concepts of is exhausted by the purely phenomenal, or that we can determine these concepts simply by gazing at a colour. Taking account of physics will lead, as Westphal argued, instead to a view about white and the other colour terms like Putnam's account of gold. Necessary truths about colours cannot be explained without reference to the logic of the compossibility of what is given in reflection and absorption spectra, the analogue of H2O.
Predicting depression in women: the role of past and

present vulnerability
Authors: BIFULCO A. , BROWN G. W. , MORAN P. , BALL C. , CAMPBELL C.
Published: July 2002

Background. A prospective study, covering just over a

1-year period, sought to confirm an earlier

finding that around 40% of women who experience a severe life event

in the presence of two

ongoing psychosocial vulnerability factors, (negative close

relationships and low self-esteem) will

develop a major depressive episode. Distal risk factors were examined

to see if they improved prediction.

Methods. A population sample of 105 mainly working-class

mothers with vulnerability and without

depression were interviewed three times over a 14-month period to

date the occurrence of severe life

events and onset of major depression. Degree of vulnerability was

assessed at first contact together

with distal risk in terms of childhood neglect/abuse

and any earlier episodes of depression.

Results. Thirty-seven per cent of these vulnerable women

became depressed in the study period. The

majority experienced a severe life event, and of these, 48% had onsets.

Contrary to expectation, risk

was only a little less among those with just one of the two

vulnerability factors. Two-thirds of

women with an onset had been depressed in previous years. Although

this was associated with

increased risk, the effect was greatest for those who had experienced

an episode before age 20. A

relationship between childhood neglect/abuse and onset was

entirely accounted for by such early depression.

Conclusion. An aetiological model of depression outlined

in earlier research was confined with a new

factor of teenage depression shown to increase risk of onset.