bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct numerical simulations of the turbulence

evolution in a uniformly sheared and stably stratified flow
Authors: JACOBITZ FRANK G. , SARKAR SUTANU , VAN ATTA CHARLES W.
Published: July 2002

Direct numerical simulations (DNS) are performed to investigate

the evolution of

turbulence in a uniformly sheared and stably stratified flow. The

spatial discretization

is accomplished by a spectral collocation method, and the solution is advanced
in

time with a third-order Runge–Kutta scheme. The turbulence evolution

is found to depend strongly on at least three parameters: the gradient

Richardson number Ri,

the initial value of the Taylor microscale Reynolds number

Reλ, and the initial value

of the shear number SK/<ε. The effect

of each parameter is individually studied while

the remaining parameters are kept constant. The evolution of the turbulent
kinetic

energy K is found to follow approximately an exponential law.

The shear number SK/<ε, whose effect has not been investigated

in previous studies, was found to have

a strong non-monotone influence on the turbulence evolution. Larger values
of the

shear number do not necessarily lead to a larger value of the eventual
growth rate

of the turbulent kinetic energy. Variation of the Reynolds number

Reλ indicated that

the turbulence growth rate tends to become insensitive to

Reλ at the higher end of

the Reλ range studied here. The

dependence of the critical Richardson number Ricr,

which separates asymptotic growth of the turbulent kinetic

energy K from asymptotic

decay, on the initial values of the Reynolds number

Reλ and the shear number SK/<ε

was also obtained. It was found that the critical Richardson number varied
over the

range 0.04<Ricr<0.17 in our

DNS due to its strong dependence on Reynolds and shear numbers.
Turbulence-induced rectified flows in rotating fluids
Authors: ZHANG XIUZHANG , BOYER DON L. , FERNANDO HARINDRA J. S.
Published: July 2002

Laboratory experiments dealing with Reynolds stress gradients

in shear-free turbulence

in homogeneous rotating fluids were conducted to better understand associated

physical phenomena. The study was motivated by possible applications to
the oceanic

environment where such Reynolds stress gradients are ubiquitous (e.g. in
the vicinity

of the continental shelf break, where turbulence decays away from the boundary).
The

turbulence was generated by vertical oscillations of a circular shaft with O-ring surface

roughness elements; the oscillation axis coincided with the axis of symmetry
of the

cylindrical test cell.

In the absence of background rotation, the turbulence is strong in the
immediate

vicinity of the shaft surface and decays with the radial distance,

r. The turbulence in the boundary layer is such that

ur∼uθ∼w,

where ur, uθ, w

are the radial, azimuthal

and vertical r.m.s. velocity components, respectively. These velocity components
are

found to be proportional to Sω, where S and

ω are the stroke and frequency of the shaft

oscillations, respectively, i.e. much the same as for the case of oscillating-grid

turbulence, which has been studied extensively.

When background rotation is present, the steady-state turbulent intensity
close to

the shaft is similar to that of the non-rotating experiments. Away from

the shaft, in the

central portion of the test cell, large-scale motions containing randomly
distributed

cyclonic and anticyclonic vortices are developed owing to small local Rossby
numbers.

In the vicinity of the shaft, a rectified anticyclonic flow Uθ is observed. The magnitude

of Uθ is found to be proportional to the

characteristic r.m.s. turbulence velocity u, but

independent of the rate of background rotation.

Consideration of the equations of motion shows that mean flows should
not be

expected if background rotation is absent. With rotation, however, the
equations

indicate that the turbulent stresses can initiate, further develop and

then maintain a

mean anticyclonic (rectified) flow around the cylinder; the azimuthal momentum

equation is shown to play a critical role in the generation of the mean

anticyclonic flow.
Vaporizing gravity currents in a superheated porous medium
Authors: WOODS ANDREW W.
Published: July 2002

We analyse the motion of a current of water migrating under gravity
into a hot
vapour-saturated porous rock accounting for the vaporization which occurs
as the
water invades the hot rock. We present a series of similarity solutions
to describe
the rate of advance of both planar and axisymmetric currents when the total
mass
of water injected after time t is proportional to
tγ. Three distinct cases arise. When
γ>1/2 (planar) or γ>1 (axisymmetric), the
depth of the current increases at all
points from the source, and therefore vaporization occurs at all points
on its surface.
This case is described by a simple extension of the well-known similarity
solutions
for non-vaporizing currents. When 0<γ<1/2 (planar)
or 0<γ<1 (axisymmetric),
there is a region near the source where the depth of the current decreases.
The depth
only increases at the more distant points. Vaporization therefore only
occurs in the
leading part of the current where it is advancing into the superheated
rock. In this
case, we develop modified similarity solutions which account for the vaporization
in
the distal part of the current. The third case involves the finite release
of fluid. Owing
to the vaporization, the mass of the current decreases with time. Since
there is no
injection, the rate of advance of the current can no longer be found by
comparing the
exponents of time in the local and global equations for mass conservation.
Instead,
the motion is described by a class of similarity solutions of the second
kind, analogous
to those described by Barenblatt (1997), in which the total mass of the
current is
proportional tγ, where γ is a
function of the mass fraction which vaporizes,
[Fscr ], such that γ→0 as [Fscr ]→0 and γ→−1
as
[Fscr ]→1. The model is extended to include the effects of capillary
retention of fluid
in the pore spaces and we discuss the relevance of our results to the process
of liquid
reinjection in the geothermal power industry.
Convective versus absolute instability in mixed
Rayleigh–Bénard–Poiseuille convection
Authors: CARRIÈRE PHILIPPE , MONKEWITZ PETER A.
Published: July 2002

Transition from convective to absolute instability in Rayleigh–Bénard
convection in
the presence of a uni-directional Poiseuille flow is studied. The evaluation
of the long-time behaviour of the Green function in the horizontal plane allows the
determination
of regions of convective and absolute instability in the Rayleigh–Reynolds
number
plane as a function of Prandtl number. It is found that the mode reaching
zero
group velocity at the convective–absolute transition always corresponds
to transverse
rolls, while the system remains convectively unstable with respect to pure
streamwise
(longitudinal) rolls for all non-zero Reynolds numbers. Finally, the roll
pattern within
the entire wave packet and in particular near its centre is elucidated
and possible
connections between experiments and our findings are discussed.
Scattering of acoustic waves by a vortex
Authors: FORD RUPERT , LLEWELLYN SMITH STEFAN G.
Published: July 2002

We investigate the scattering of a plane acoustic wave by an axisymmetric vortex in
two dimensions. We consider vortices with localized vorticity, arbitrary circulation and
small Mach number. The wavelength of the acoustic waves is assumed to be much
longer than the scale of the vortex. This enables us to define two asymptotic regions:
an inner, vortical region, and an outer, wave region. The solution is then developed
in the two regions using matched asymptotic expansions, with the Mach number
as the expansion parameter. The leading-order scattered wave field consists of two
components. One component arises from the interaction in the vortical region, and
takes the form of a dipolar wave. The other component arises from the interaction in
the wave region. For an incident wave with wavenumber k propagating in the positive
X-direction, a steepest descents analysis shows that, in the far-field limit, the leading-order scattered field takes the form
i(π−θ)eikX+½cosθcot(½θ)
(2π/kR)1/2ei(kR−π/4),
where θ is the usual polar angle. This expression is not valid in a parabolic region
centred on the positive X-axis, where kRθ2=O(1).
A different asymptotic solution is appropriate in this region. The two solutions match onto
each other to give a leading-order scattering amplitude that is finite and single-valued
everywhere, and that vanishes along the X-axis. The next term in the expansion in
Mach number has a non-zero far-field response along the X-axis.
Analysis of mixing in three-dimensional time-periodic cavity flows
Authors: ANDERSON P. D. , GALAKTIONOV O. S. , PETERS G. W. M. , VAN DE VOSSE F. N. , MEIJER H. E. H.
Published: July 2002

A method to locate periodic structures in general three-dimensional Stokes flows
with time-periodic boundary conditions is presented and applied to mixing cavity
flows. Numerically obtained velocity fields and particle tracking schemes are used to
provide displacement and stretching fields. From these the location and identification
of periodic points can be derived. The presence or absence of these periodic points
allows a judgement on the quality of the mixing process. The technique is general
and efficient, and applicable to mixing flows for which no analytical velocity field is
available (the case for all three-dimensional flows considered in this paper). Results
are presented for three different mixing protocols in a three-dimensional time-periodic
cavity flow, serving as an accessible test case for the methods developed. A major
result is that periodic lines are obtained for these three-dimensional flows. These lines
can be complex in geometry and their nature can change along a line from hyperbolic
to elliptic. They can serve as practical criteria in the optimization of three-dimensional
mixing processes.
Thermosolutal bifurcation phenomena in porous
enclosures subject to vertical temperature and
concentration gradients
Authors: MAMOU M. , VASSEUR P.
Published: July 2002

The Darcy model with the Boussinesq approximations is used to study double-diffusive
instability in a horizontal rectangular porous enclosure subject to two sources of
buoyancy. The two vertical walls of the cavity are impermeable and adiabatic while
Dirichlet or Neumann boundary conditions on temperature and solute are imposed on
the horizontal walls. The onset and development of convection are first investigated
using the linear and nonlinear perturbation theories. Depending on the governing
parameters of the problem, four different regimes are found to exist, namely the
stable diffusive, the subcritical convective, the oscillatory and the augmenting direct
regimes. The governing parameters are the thermal Rayleigh number, RT, buoyancy
ratio, N, Lewis number, Le, normalized porosity of the porous medium,
ε, aspect ratio of the enclosure, A, and the thermal and solutal
boundary condition type, κ,
applied on the horizontal walls. On the basis of the nonlinear perturbation theory
and the parallel flow approximation (for slender or shallow enclosures), analytical
solutions are derived to predict the flow behaviour. A finite element numerical method
is introduced to solve the full governing equations. The results indicate that steady
convection can arise at Rayleigh numbers below the supercritical value, indicating
the development of subcritical flows. At the vicinity of the threshold of supercritical
convection the nonlinear perturbation theory and the parallel flow approximation
results are found to agree well with the numerical solution. In the overstable regime,
the existence of multiple solutions, for a given set of the governing parameters, is
demonstrated. Also, numerical results indicate the possible occurrence of travelling
waves in an infinite horizontal enclosure.
Non-axisymmetric vortices in two-dimensional flows
Authors: LE DIZÈS STÉPHANE
Published: July 2002

Slightly non-axisymmetric vortices are analysed by asymptotic methods in the context
of incompressible large-Reynolds-number two-dimensional flows. The structure of the
non-axisymmetric correction generated by an external rotating multipolar strain field
to a vortex with a Gaussian vorticity profile is first studied. It is shown that when the
angular frequency w of the external field is in the range of the angular velocity of
the vortex, the non-axisymmetric correction exhibits a critical-point singularity which
requires the introduction of viscosity or nonlinearity to be smoothed. The nature of
the critical layer, which depends on the parameter
h = 1/(Re ε3/2), where ε is the
amplitude of the non-axisymmetric correction and Re the Reynolds number based on
the circulation of the vortex, is found to govern the entire structure of the correction.
Numerous properties are analysed as w and h vary for a multipolar strain field of
order n = 2, 3, 4 and 5. In the second part of the paper, the problem of the existence
of a non-axisymmetric correction which can survive without external field due to the
presence of a nonlinear critical layer is addressed. For a family of vorticity profiles
ranging from Gaussian to top-hat, such a correction is shown to exist for particular
values of the angular frequency. The resulting non-axisymmetric vortices are analysed
in detail and compared to recent computations by Rossi, Lingevitch & Bernoff (1997)
and Dritschel (1998) of non-axisymmetric vortices. The results are also discussed
in the context of electron columns where similar non-axisymmetric structures were
observed (Driscoll & Fine 1990).
Shear flow over a self-similar expanding
pulmonary alveolus during rhythmical breathing
Authors: HABER S. , BUTLER J. P. , BRENNER H. , EMANUEL I. , TSUDA A.
Published: July 2002

Alternating shear flow over a self-similar, rhythmically expanding hemispherical depression
is investigated. It provides a fluid-mechanical model for an alveolated respiratory
unit, by means of which the effect of lung rhythmical expansion on gas mixing
as well as aerosol dispersion and deposition can be studied. The flow is assumed to
be very slow and governed by the quasi-steady linear Stokes equations. Consequently,
superposition of the following two cases provides an easy route toward characterizing
the aforementioned flow field. The first case treats the flow field that is generated
by a rhythmically expanding spherical cap (the alveolus). The cap is attached at its
rim to a circular opening in an expanding unbounded plane bounding a semi-infinite
fluid region. The rate of expansion of the cap and the plane are chosen such as to
maintain the system's configurational self-similarity. The second case addresses the
flow disturbance that is generated by an alternating shear flow encountering a rigid
hemispherical cavity in a plane bounding a semi-infinite fluid domain.

For the first case, a stream-function representation employing toroidal coordinates
furnishes an analytical solution, whereas the second case was solved numerically by
Pozrikidis (1994). Linear superposition of the two flow cases results in particularly
rich streamline maps. In the symmetry plane (bisecting the cap and parallel to the
mean shear flow), for a certain range of shear to expansion-rate ratios, the streamline
maps are self-similar and display closed orbits and two internal stagnation points.
One of the stagnation points is a ‘centre’ surrounded by closed streamlines whereas
the other constitutes a ‘saddle point’. For other planes, no stagnation points exist in
the field, but the streamlines associated with the saddle point display complex looping
patterns. These unique flow structures, when subjected to a small perturbation (e.g. a
small asynchrony between ductal and alveolar entering flows) cause highly complex
stochastic particle trajectories even in the quasi-static Stokes alveolar flow. The
observed irreversible flow phenomena in a rhythmically expanding alveolus may be
partially responsible for the ‘stretch-and-fold’ flow mixing patterns found in our recent
flow visualization studies performed in excised animal lung acini.
Labour Policy, Labour–Business Relations and the Transition to Democracy in Chile
Authors: S. BARRETT PATRICK
Published: July 2002

Chile's new civilian government, the centre-left Concertación de Partidos por la Democracia, has been strongly praised for its efforts to strengthen the rights of labour and correct Chile's severe social inequalities. After nearly a decade of civilian rule, however, it has become increasingly clear that these efforts have not succeeded. Indeed, one of the defining features of Chile's new democracy is the profound inequality and imbalance of power between capital and labour upon which it has been constructed. This article seeks to explain this outcome and examine its implications for Chile's post-military political and economic order.
The First Ambassadors: Cuba's Contribution to

Guinea-Bissau's War of Independence
Authors: GLEIJESES PIERO
Published: July 2002

As the rebels of Guinea-Bissau fought for independence from

Portugal, Cuban military instructors stood by their side and Cuban

doctors treated their wounds. Joining the rebellion in 1966, and

remaining through the war's end in 1974, this was the longest

Cuban intervention in Africa before the despatch of troops to Angola

in November 1975. It was also the most successful. As the Guinean

paper Nõ Pintcha declared, ‘The Cubans'

solidarity was decisive for our struggle’. Cuba's

contribution to Guinea-Bissau's war of independence is an

important and revealing example of Cuban policy in Africa.
Struggling against Decline: British Business in Chile, 1919–33
Authors: BARTON JONATHAN R.
Published: July 2002

British business in Latin America struggled throughout the inter-war
period, affected by the First World War, aggressive US trade strategies and a
dated British commercial support structure that had turned its attentions to
imperial markets. Chamber of Commerce archive material reveals the frustrations
of the British business community in Chile as hard-won markets were lost to well-supported US firms and returning German competition, as a consequence of
weak political, financial and marketing support. Against a backdrop of British
commercial decline worldwide, the Chilean case echoes the experiences of
businessmen across Latin America's non-imperial markets. As the British
government dallied, US business established an unassailable position.
The collapse of Zaïre: implosion,
revolution or external sabotage?
Authors: McNulty Mel
Published: July 2002

The collapse of Mobutu's Zaïre in 1996/97 was the
result of an unprecedented
correspondence of domestic, regional and international interests.
The Zaïrean state was established and sustained during the Cold War
with
Western support as a bulwark against communism and source of raw materials.

It maintained itself after the Cold War by playing on external fears of
state
collapse and by supporting French regional interests. By 1996, with the

failure of French credibility and US refusal to intervene, it had no reliable

external protector. Internal support was non-existent, and an opposition

alliance was constructed under Kabila's leadership. Regional states,

notably Rwanda and Angola, intervened to protect their own security.
Though successful, this regional alliance itself proved to be unstable,
leading
to a recurrence of war in 1998.
Parametric coupling of light waves and a
surface polariton in a plasma bounded by free space
Authors: LEE HEE J. , MUN BYUNG-SUK
Published: July 2002

We investigate a three-wave decay interaction involving a surface
wave in which a bulk electromagnetic plasma wave decays into another bulk
electromagnetic plasma wave and a surface polariton. It is shown that a p-polarized
light wave transmitted from vacuum into a plasma at a particular
angle of incidence can propagate as a bulk electromagnetic plasma wave
without attenuation. The nonlinear boundary conditions for the surface wave
are formulated in terms of the surface charge and the volume current, taking
full account of the rippling of the free boundary. The coupled-mode equations
are derived and solved in the parametric approximation to obtain the threshold
and the growth rate. We assess the relative strength of the kinematic and the
dynamic nonlinearities in the parametric interaction.
Arc-liberated chemical energy exceeds electrical input energy
Authors: GRANEAU PETER , GRANEAU NEAL , HATHAWAY GEORGE , HULL RICHARD L.
Published: July 2002

This paper reports the first experimental results in which the kinetic
energy of cold fog, generated in a water arc plasma, exceeds the electrical
energy supplied to form and maintain the arc. The cold fog explosion is
produced by breaking down a small quantity of liquid water and passing a
kiloampere current pulse through the plasma. The 90-year history of unusually
strong water arc explosions is reviewed. Experimental observations leave little
doubt that internal water energy is being liberated by the sudden electrodynamic
conversion of about one-third of the water to dense fog. High-speed
photography reveals that the fog expels itself from the water at supersonic
velocities. The loss of intermolecular bond energy in the conversion from liquid
to fog must be the source of the explosion energy.
A method for recording predator–prey encounters between crabs and limpets using wax replicas
Authors: Thompson R.C. , Jenkins S.R. , Bussell J.A.
Published: July 2002

This study examined the use of replica limpets made from modelling wax to provide an index of encounter frequency between crabs and their limpet prey. Video observations at Port Erin Marine Laboratory, showed that the intertidal crabs, Carcinus maenas (L.), Necora puber (L.) and to a lesser extent Cancer pagarus L., regularly examined and tried to remove both real and replica limpets with their chelae. Replica limpets became scratched or gouged as a result of these encounters. The frequency of attack was similar for both real and replica limpets. Hence marks on the limpet models provided a reliable index of attacks on real limpets. The frequency, timing and spatial distribution of encounters between limpets and crabs were recorded by scoring the marks made on model limpets deployed amongst real limpets on the shore. During a 28-day period at Port St Mary on the Isle of Man, limpet models were marked more frequently and with longer scratches on the lower shore than on the upper shore, suggesting that larger crabs were present on the lower shore. Models, deployed at Prawle Point, Devon, showed that encounters between crabs and limpets occurred during both day and night-time high tides. The models were durable and provided an inexpensive method for recording encounters between crabs and limpets. Some replicas were also marked by the teeth of small fish and rodents. Model prey such as these could also be used to study other predator–prey encounters, particularly in conditions which preclude direct observation or video recording, or for use with animals that might be disturbed by observers or cameras.
Autoecology and morphological variability of Dinophysis sacculus (Dinophyceae: Dinophysiaceae) in a Mediterranean lagoon
Authors: Caroppo C.
Published: July 2002

Dinophysis sacculus (Dinophyceae) is a potential producer of diarrhoeic shellfish poisoning (DSP). Population dynamics of this dinoflagellate was followed in the Varano lagoon, south-east Italy, with the objective of determining the seasonal abundance of D. sacculus and the relationship to environmental factors. The seasonal occurrence of this dinoflagellate showed a rather wide temporal distribution and increases in cell numbers were observed in late June and November. Dinophysis numbers seasonal changes appeared to be dependent on chemico–physical factors and dissolved nutrients. Three morphologically distinct forms of D. sacculus were found during the sampling period (March 1997–February 1998) related to the life history of the species and not to environmental conditions. In this mussel fishery, D. sacculus presence and proliferation were not associated with biotoxicity.
Grazing activity of mesoplanktonic copepods in a shallow bay during an algal spring bloom (Marennes-Oléron Bay, France)
Authors: Sautour Benoît , Castel Jacques
Published: July 2002

In situ grazing activity of mesoplanktonic copepods was investigated by the fluorometric method during an algal spring bloom in a zone of oyster farming in Marennes-Oléron Bay. The grazing activity of copepods was overall higher during the night than during the day for three species (Temora longicornis, Paracalanus parvus and Acartia clausi), but peaks also appeared during the day for all of them. Individual ingestion rates and daily rations were higher during neap tide (low suspended particulate matter (SPM) concentrations) than during spring tide (high SPM concentrations). During ebb tide (when SPM concentrations were the lowest) the feeding activity of T. longicornis, P. parvus and A. clausi was significantly negatively correlated with algal concentration. Our work suggests that during the algal spring bloom in the farming area of Marennes-Oléron Bay the pressure exerted by mesoplanktonic copepods on the algal stock was very low, as a consequence of: (i) high algal concentrations in the field (resuspension and high phytoplanktonic production); (ii) low ingestion rates when high algal concentrations were observed. The likely ingestion of non-fluorescent particles by copepods is discussed.
Put out the light, and then put out the light
Authors: Raven J.A. , Kübler J.E. , Beardall J.
Published: July 2002

The lowest photon flux density of photosynthetically active radiation at which O2-evolving marine photolithotrophs appear to be able to grow is some 10 nmol photon m−2 s−1, while marine non-O2-evolvers can grow at 4 nmol photon m−2 s−1, in both cases with the photon flux density averaged over the 24 hour L:D cycle. Constraints on the ability to grow at very low fluxes of photosynthetically active radiation fall into three categories. Category one includes essential processes whose efficiency is independent of the rate of energy input, but whose catalysts show phylogenetic variation leading to different energy costs for a given process in different taxa, e.g. light-harvesting complexes, RUBISCO and probably in the sensitivity of PsII to photodamage. The second category comprises essential processes whose efficiency decreases with decreasing energy input rate as a result of back-reactions independent of the energy input rate, e.g. charge recombination following charge separation by PsII and short-circuit H+ fluxes across the thylakoid membrane which decrease the fraction of pumped H+ which can be used in adenosine diphosphate phosphorylation. Category two also includes that component of protein turnover which cannot be related to replacement of polypeptides which were incorrectly assembled following uncorrected errors of transcription or translation, or which were damaged by processes whose rate increases with increasing energy input rate such as photodamage to PsII. The third category includes only O2-dependent damage to the D1 protein of PsII whose rate increases with a decreasing incident flux of photosynthetically active radiation. Processes in categories two and three are most likely to impose the lower limit on the photon flux density which can support photolithotrophic growth. The available literature, mainly on organisms which are not adapted to growth at very low photon flux densities, suggests that three major limitations (charge recombination in PsII, H+ leakage and slippage, and protein turnover) can individually impose lower limits in excess of 20 nmol photon m−2 s−1 on photolithotrophic growth. Furthermore, these three limitations are interactive, so that considering all three processes acting in series leads to an even higher predicted lower photon flux density limit for photolithotrophic growth.
Membrane localization and demonstration of isoforms of nucleoside triphosphate hydrolase from Toxoplasma gondii
Authors: KIKUCHI T. , FURUTA T. , KOJIMA S.
Published: July 2002

Toxoplasma gondii has a unique enzyme, a NTPase, which has a wide specificity toward NTP. In the present study, we produced a monoclonal antibody (IgG1, 6C6) against the enzyme which could recognize NTPase isozymes among several strains of T. gondii. Three avirulent strains of T. gondii, ME49, Beverley and Nakayama, were found to have 1 NTPase (63kDa, pI 6·0), while a virulent strain RH and an avirulent strain Fukaya had 2 isozymes (63kDa) with different pIs (pIs 6·0 and 6·5 for the former, and pIs 6·2 and 6·4 for the latter, respectively), suggesting that this monoclonal antibody recognizes a common epitope of NTPase among T. gondii strains. Furthermore, 6C6 could inhibit NTPase activity in the presence of dithiothreitol in a dose-dependent manner, and immuno-EM study of NTPase revealed that this molecule is located on the surface membrane of T. gondii tachyzoites. When Vero cells were co-cultured with tachyzoites pre-treated with 6C6, the number of infected cells significantly decreased, suggesting that 6C6 inhibits invasion of the parasites to host cells. These data suggest that the molecule recognized by 6C6 might be considered a potential candidate antigen for vaccines against T. gondii tachyzoites.
Introduction: Opportunities to work together: intestinal helminth control and programmes to eliminate lymphatic filariasis
Authors: CLINE B.L. , SAVIOLI L. , NEIRA M.
Published: July 2002

The purpose of this brief introduction to the
supplement that follows is to highlight the current
unique opportunity to coordinate intestinal helminth
control programmes with the relatively new global
initiative to eliminate lymphatic filariasis. Such
synergy at global, regional, national and local levels
has the potential to greatly enhance the impact,
decrease the cost and facilitate sustainability in both
of these health programmes.
Anti-oxidant enzymes in Cryptosporidium parvum oocysts
Authors: ENTRALA E. , MASCARO C. , BARRETT J.
Published: July 2002

Oocysts of Cryptosporidium parvum showed relatively low
levels of SOD activity. The SOD which had a pI of 4.8 and an approximate
molecular weight of 35 kDa appeared to be iron dependent. Catalase, glutathione
transferase, glutathione reductase and glutathione peroxidase activity
could not be detected, nor could trypanothione reductase. No NADH or NADPH
oxidase activity could be detected, nor could peroxidase activity be demonstrated
using o-dianisidine, guaiacol, NADPH or NADH as co-substrates.
However, an NADPH-dependent H2O2 scavenging system
was detected in the insoluble fraction.
Ultrastructural investigation of the secondary excretory
system in different stages of the procercoid of
Triaenophorus nodulosus (Cestoda, Pseudophyllidea, Triaenophoridae)
Authors: KORNEVA J. V. , KUPERMAN B. I. , DAVYDOV V. G.
Published: July 2002

The formation of the definitive procercoid excretory system of

the pseudophyllidean cestode Triaenophorus nodulosus has
been investigated. This process can be divided into 3 main stages. In
the first stage, active autophagic processes lead to
the formation of intracellular excretory canals. In the second stage,
the process of the autolysis is enhanced and the system
of intercellular lacunae functioning as an excretory system is formed.

A definitive excretory system of the procercoid forms
at the next stage, by means of the migration and proliferation of
undifferentiated cells replacing the lacunar system.
Neurophysiology of glutamatergic signalling and
anthelmintic action in Ascaris suum: pharmacological
evidence for a kainate receptor
Authors: DAVIS R. E.
Published: July 2002

Electrophysiological and pharmacological techniques were used
to study glutamatergic signalling in the parasitic nematode, Ascaris
suum.
Glutamate or kainate injections into whole worms produced a paralysed quasi-static

posture similar to the waveform in behaving worms. The DE2 motorneuron
class
is a primary target. Several glutamatergic substances
produced pronounced conductance increases and depolarization in DE2; domoate

and kainate were the most potent
agonists tested. Glutamate responses and spontaneous excitatory post-synaptic

potentials in DE2 were reversibly blocked
in sodium-free saline. DE2 sensitivity to exogenous glutamate was
sustained during block of synaptic transmission
suggesting that glutamatergic receptors are located on DE2 neurons. The

glutamate-induced response was localized to the
DE2 dendrite, coincident with the synapses responsible for spontaneous

potentials in DE2. Steady-state potentials reached
during glutamate superfusion were similar to the reversal potentials for

both the spontaneous post-synaptic potentials and
glutamate, also suggesting that these potentials may be glutamatergic.

Non-N-methyl-D-aspartate receptor antagonists
partially blocked spontaneous DE2 excitatory potentials and responses
elicited by exogenous glutamate and kainate. This
glutamatergic pathway may play a role in nematode locomotory behaviour

and account for the paralysing anthelmintic
action of excitatory amino acid analogues like kainate and domoate.
Electrorotation and dielectrophoresis
Authors: GOATER A. D. , PETHIG R.
Published: July 2002

Using microelectrode structures, various forms of electric fields, such as non-uniform, rotating and travelling wave, can
be imposed on particles of sizes ranging from proteins and viruses to micro-organisms and cells. Each type of particle
responds to the forces exerted on them in a unique way, allowing for their controlled and selective manipulation as well
as their characterization. Moreover, particles of the same type but of different viability can be distinguished in a simple,
reliable manner. This review outlines the principles that govern the way in which bioparticles respond to these various
field types, and how they can be exploited. Examples of current and potential biotechnological and biomedical applications
are given, along with a critical comparison of current techniques.
Compatibility of Schistosoma mansoni and
Biomphalaria pfeifferi in Northern Senegal
Authors: TCHUEM TCHUENTÉ L. A. , SOUTHGATE V. R. , THÉRON A. , JOURDANE J. , LY A. , GRYSEELS B.
Published: July 2002

The construction of the Diama dam on the Senegal River and the ensuing ecological changes have led to a massive outbreak
of Schistosoma mansoni infection in Northern Senegal, associated with very high intensity of infections, due to extremely
intense transmission. The vectorial capacity of Biomphalaria pfeifferi from Ndombo, near Richard-Toll was investigated
in order to assess the role of the snail–parasite relationship in this particular epidemiological situation. The results revealed
an unusually high compatibility between the Senegalese S. mansoni strain and its local snail intermediate host, B. pfeifferi.
The snail infection rate after exposure to a single miracidium per snail was 87%. The cercarial production of infected
snails was very high, with a mean total production of 50456 cercariae per snail. No significant difference was found in the
total cercarial output between snails exposed to 1 miracidium and those exposed to 5 miracidia. The increase in the rate
of cercarial output was significantly greater in snails exposed to 5 miracidia, but there was a higher mortality in this group.
The chronobiological cercarial production pattern showed a peak around mid-day. The implications of these findings on
the epidemiology of schistosomiasis in Northern Senegal are discussed.
Cloning and analysis of a Trichinella britovi gene encoding
a cytoplasmic heat shock protein of 72 kDa
Authors: VAYSSIER M. , LE GUERHIER F. , FABIEN J. F. , PHILIPPE H. , VALLET C. , ORTEGA-PIERRES G. , SOULE C. , PERRET C. , MINGYUAN LIU , VEGA-LOPEZ M. , BOIREAU P.
Published: July 2002

A gene encoding a protein of 646 amino acid residues with a molecular mass of 71·3 kDa showing homology to the
cytoplasmic form of the 70 kDa heat shock protein was cloned and sequenced from the nematode parasite Trichinella
britovi (Tb). The gene was expressed in vitro as a protein of 71 kDa that was immunoprecipitated by a Trichinella-infected
rabbit serum. Monospecific polyclonal antibodies raised against the recombinant Tb Hsp70 expressed in Escherichia coli,
recognized a protein of 70 kDa by Western blot analysis of Tb soluble antigen (muscular stage). Tb Hsp70 was located
in the nuclei of the muscle larvae as determined by the indirect immunofluorescent pattern on cross-sections of the worm.
The expression of this protein was not detected in adult worm nuclei suggesting a differential expression of Hsp70 between
the 2 stages of Trichinella.
Survival and transmission of Anguillicola crassus
Kuwahara, Niimi & Itagaki, 1974 (Nematoda)
in seawater eels
Authors: KIRK R. S. , LEWIS J. W. , KENNEDY C. R.
Published: July 2002

The study aims were to quantify the survivorship of Anguillicola crassus in eels in seawater and investigate transmission
in estuarine (50% seawater) and marine (100% seawater) simulated conditions. Most A. crassus were able to survive and
reproduce in 50% and 100% seawater eels for up to 6 months and therefore could survive during the spawning migration
of eels to the Sargasso Sea. Up to 10% of the parasite metapopulation were damaged after long-term exposure to 50% or
100% seawater. Transmission of A. crassus was completed in 50% and 100% seawater in the laboratory, although
infection levels in 100% seawater hosts were always lower. Transmission in estuaries is ecologically possible since the
copepod Eurytemora affinis is susceptible to infection and is the dominant autochthonous species in most tidal estuaries
in the Northern hemisphere. Transmission at sea is unlikely due to lack of suitable intermediate hosts. The data support
the suggestion that dissemination of A. crassus has been facilitated by natural movement of eels in coastal waters. It is
possible that A. crassus could impair the success of the eel spawning migration to the Sargasso Sea, although there is no
direct evidence to support this.
Prospects for controlling animal parasitic nematodes by predacious micro fungi
Authors: LARSEN M.
Published: July 2002

Resistance against anthelmintics is widespread, particularly in parasitic nematode populations of small ruminants. Several
new techniques or supplements have been developed or are under investigation. Biological control (BC) is one of these
new methods. The net-trapping predacious fungus Duddingtonia flagrans produces thick walled resting spores,
chlamydospores, which are able to survive passage through the gastrointestinal tract of cattle, horses, sheep and pigs. Under Danish
climatic conditions it has been shown that the number of parasite larvae on pasture and the worm burden of the grazing
animals is significantly reduced when animals are fed spores during the initial 2–3 months of the grazing season. Work
with D. flagrans in France, Australia, USA, and Mexico has confirmed the strong BC potential of this fungus. Today
much work is going into development of suitable delivery systems for grazing livestock worldwide. Ultimately, BC should
be implemented in integrated parasite control strategies, both in conventional and organic livestock production.
In vitro activity of the polyether ionophorous antibiotic monensin against the cyst form of Toxoplasma gondii
Authors: COUZINET S. , DUBREMETZ J. F. , BUZONI-GATEL D. , JEMINET G. , PRENSIER G.
Published: July 2002

We have studied the activity of the polyether ionophorous antibiotic monensin against the cyst form (bradyzoite) of
Toxoplasma gondii. The experiments were conducted in vitro using 2 methods; cysts produced either in mice or in cell
culture were exposed to monensin in vitro, and the infectivity of the parasites was then assessed in vivo or in vitro. The
data obtained from these 2 systems of evaluation showed that monensin inhibits the infectivity and the viability of the
bradyzoites. Its activity was time and concentration dependent. The first effects were observed at very low drug
concentrations (i.e. 0·0001 μg/ml). Immunofluorescence and electron microscopy analysis showed significant cytological
alterations of the monensin-treated bradyzoites: they were swollen, had a large number of vacuoles in their cytoplasm and
were found lysed at higher concentrations in ionophore.
Was Wittgenstein a Plagiarist?
Authors: Cohen Michael
Published: July 2002

Laurence Goldstein has ‘re-created’ Wittgenstein's doctoral viva, arguing that had Wittgenstein's dissertation, his Tractatus Logico-Philosophicus, ‘been judged by normal standards of originality and philosophical argumentation, it would have failed’. Goldstein claims that Wittgenstein ‘lifted’ central doctrines from Russell and from Bernard Bolzano. I point out that passages allegedly plagiarized from Russell are actually criticisms of his doctrines, and that there is no evidence that Wittgenstein even knew Bolzano's work, directly or indirectly. I argue that alleged similarities, substantial and stylistic, between his work and Bolzano's give no support even to a weaker claim of influence.
Is There Anything it is Like to be a Bat?
Authors: Hacker P. M. S.
Published: July 2002

The concept of consciousness has been the source of much confusion over the past two decades. Current orthodoxy in ‘consciousness studies’ has it that the key to understanding the concept of consciousness is to grasp the idea of qualia. But the appearance of mystery here is the product of conceptual confusion. There is nothing to ‘the qualitative character of experience’ beyond the individual character of a specific experience and how the subject felt in undergoing it, and here there are no mysteries beyond empirical ignorance and conceptual mystification.
Electro-convulsive therapy practices in the community
Authors: PRUDIC J. , OLFSON M. , SACKEIM H. A.
Published: July 2002

Background. Controlled studies have demonstrated that variations in electro-convulsive therapy (ECT) technique impacts on efficacy and cognitive side effects. However, there is little information on the extent of variation in how ECT is practiced in community settings in the United States.

Methods. A survey of practice patterns was conducted at ECT facilities in the greater New York City metropolitan area.

Results. The 59 facilities varied considerably in many aspects of ECT practice, often clearly departing from the standards in the field. The more intensive the form of ECT used at facilities, the less likely was cognitive status assessed following the treatment course.

Conclusion. There is marked variability in the nature of ECT practices in community settings. The extent to which this variability impacts on the benefits and risks of ECT needs to be examined.
Three- to 5-year prospective follow-up of outcome in major depression
Authors: VAN LONDEN L. , MOLENAAR R. P. G. , GOEKOOP J. G. , ZWINDERMAN A. H. , ROOIJMANS H. G. M.
Published: July 2002

Background. A Dutch cohort of predominantly out-patient
DSM-III-R
major depressive patients
was followed for 3 to 5 years after start of treatment in a
psycho-neuro-endocrinological prediction
study. The study design permitted description of the course of
remissions, relapses and recurrences.

Methods. Pharmacological treatment was standardized, psychotherapy

was tailored to the needs of
the patient, follow-ups were done monthly until 3 years or more after the
initial recruitment.

Results. After 9 months 49% of the patients had reached full

remission and 45% were in partial
remission. During the following 3 to 5 years 82% of the patients had reached
a period of full
remission. Sixteen per cent of the patients needed 2 years or more
before full remission. A relapse
or recurrence rate of 41% within 5 years was found. Patients with residual
symptoms relapsed
particularly in the first 4 months after remission, while patients
without residual symptoms recurred
mainly after 12 months after remission. Previous depressive episodes and
psychoticism predicted
relapse. Psychomotor retardation at inception predicted a longer time to
partial remission.

Conclusion. In most cases, major depression is a seriously

impairing episodic disease. This is also
true for a sample of predominantly out-patients treated at a university
clinic.
Is subcortical disease associated with a poor response
to antidepressants? Neurological, neuropsychological
and neuroradiological findings in late-life depression
Authors: SIMPSON S. , BALDWIN R. C. , JACKSON A. , BURNS A. S.
Published: July 2002

Background. Late-life depression is associated with
increased subcortical white matter hyper-intensities. There is some evidence

that they are associated with a poorer response to acute
treatment. Neurological signs and neuropsychological dysfunction are further
evidence of
abnormalities in the brain, but they have not been studied in relation
to therapy resistance.

Methods. A prospective study of 24 normal controls and
75 consecutive elderly (aged 65 to 85)
patients with DSM-III-R major depression entered a naturalistic study
of treatment. Assessment of
response to monotherapy and then lithium augmentation or ECT created three
outcome groups.
Investigations included magnetic resonance brain imaging, neuropsychological
and neurological
examination.

Results. Response to monotherapy within 12 weeks was
shown by 42·7%, a further 37·3%
responded to lithium augmentation or ECT within 24 weeks and 20% had responded
poorly to all
treatments at 24 weeks. Subcortical hyperintensities were significantly
increased in the more
resistant patients. These included confluent deep white matter,
multiple (>5) basal ganglia lesions
and pontine reticular formation lesions. Most of the neuropsychological

impairment was restricted
to the resistant groups and was of a subcortico-frontal type.
Extrapyramidal, frontal and pyramidal
neurological signs characterized the resistant groups. The combination
of extrapyramidal signs,
pyramidal tract signs and impairment of motor hand sequencing
strongly predicted resistance to 12
weeks of antidepressant monotherapy with 89% sensitivity and 95% specificity.

Conclusion. In late-life depression a poor response to
antidepressant monotherapy can be expected
in those patients with a frontal lobe syndrome, extrapyramidal signs or

if MRI T2-weighted lesions
are present in both the basal ganglia and the pontine reticular formation.