bluuebunny/crossref_metadata_2025 huggingface dataset:
Patterns of bubble desorption during the solidification of a multicomponent melt
Authors: ROGERSON M. A. , CARDOSO S. S. S.
Published: July 2002

The desorption of bubbles during solidification of a melt occurs in processes as
diverse as the making of ice cubes, the formation of igneous rocks and the casting of
metals. In both the metal casting and rock formation processes, careful observation of
the final solid suggests that the desorbed bubbles often form regular spatial patterns.
Understanding and quantifying the mechanisms by which such patterns arise is
important. In the geological context, comparison between field measurements and the
predictions of a model will allow geologists to estimate in-situ magma properties. In
the metal casting context, engineers would like to be able to specify mould geometries
and cooling conditions to ensure that the distribution of bubbles will not compromise
the strength of critical sections of the casting.

In the present study, we develop a detailed mathematical model to predict the
distribution of desorbed bubbles in a solidified melt. Our new model builds upon
previous knowledge on this phenomenon in the geological context (Toramaru et al.
1996, 1997). We describe desorption of a dissolved gas in a semi-infinite melt, solidified
by a one-dimensional heat flux. In the absence of convection, the transfer of heat and
solute occurs mainly by a diffusive mechanism and the crystallization proceeds most
rapidly near the cooled boundary. The crystals formed contain almost no dissolved
gas and hence the concentration of gas dissolved in the melt increases progressively
towards the cooled boundary. Diffusion of dissolved gas from the crystallizing zone is
slow and, as a result, the local melt becomes supersaturated and gas bubbles desorb.
The full equations for this coupled solidification and desorption processes are solved
numerically.

We find that bubbles desorb forming a sequence of layers parallel to the cooled
boundary. The spacing between these bubble layers increases geometrically from
the cooled boundary. We give a physical interpretation for this geometric pattern
and analyse the effect of physical parameters on the layer spacing. We show that
our theoretical model captures the important physical mechanisms involved in the
solidification and desorption processes by comparing its predictions with available
measurements from a geological formation.
The dynamics of a viscous soap film with soluble surfactant
Authors: CHOMAZ JEAN-MARC
Published: July 2002

Nearly two decades ago, Couder (1981) and Gharib & Derango (1989) used soap films
to perform classical hydrodynamics experiments on two-dimensional flows. Recently
soap films have received renewed interest and experimental investigations published
in the past few years call for a proper analysis of soap film dynamics. In the present
paper, we derive the leading-order approximation for the dynamics of a flat soap film
under the sole assumption that the typical length scale of the flow parallel to the film
surface is large compared to the film thickness. The evolution equations governing
the leading-order film thickness, two-dimensional velocities (locally averaged across
the film thickness), average surfactant concentration in the interstitial liquid, and
surface surfactant concentration are given and compared to similar results from the
literature. Then we show that a sufficient condition for the film velocity distribution
to comply with the Navier–Stokes equations is that the typical flow velocity be
small compared to the Marangoni elastic wave velocity. In that case the thickness
variations are slaved to the velocity field in a very specific way that seems consistent
with recent experimental observations. When fluid velocities are of the order of the
elastic wave speed, we show that the dynamics are generally very specific to a soap
film except if the fluid viscosity and the surfactant solubility are neglected. In that
case, the compressible Euler equations are recovered and the soap film behaves like a
two-dimensional gas with an unusual ratio of specific heat capacities equal to unity.
Secondary motion in convection layers generated
by lateral heating of a solute gradient
Authors: CHAN CHO LIK , CHEN WEN-YAU , CHEN C. F.
Published: July 2002

The three-dimensional motion observed by Chen & Chen (1997) in the convection cells
generated by sideways heating of a solute gradient is further examined by experiments
and linear stability analysis. In the experiments, we obtained visualizations and
PIV measurements of the velocity of the fluid motion in the longitudinal plane
perpendicular to the imposed temperature gradient. The flow consists of a horizontal
row of counter-rotating vortices within each convection cell. The magnitude of this
secondary motion is approximately one-half that of the primary convection cell.
Results of a linear stability analysis of a parallel double-diffusive flow model of the
actual ow show that the instability is in the salt-finger mode under the experimental
conditions. The perturbation streamlines in the longitudinal plane at onset consist
of a horizontal row of counter-rotating vortices similar to those observed in the
experiments.
Planimetric instability of channels with variable width
Authors: REPETTO R. , TUBINO M. , PAOLA C.
Published: July 2002

We study the steady three-dimensional flow field and bed topography in a channel with
sinusoidally varying width, under the assumptions of small-amplitude width variations
and sufficiently wide channel to neglect nonlinear effects and sidewall effects. The aim
of the work is to investigate the role of width variations in producing channel
bifurcation in braided rivers. We infer incipient bifurcation in cases where the growth
of a central bar leads to planimetric instability of the channel, i.e. when the given
infinitesimal width perturbation is enhanced. Results of the three-dimensional model
suggest that the equilibrium bottom profile mainly consists of a purely longitudinal
component, uniformly distributed over the cross-section, which induces deposition at
the wide section and scour at the constriction, and of a transverse component in
the form of a central bar (wide sections) and scour (constrictions), with longitudinal
wavelength equal to that of width variations. A comparison between the results of
the three-dimensional model and those obtained by means of a two-dimensional
depth-averaged approach shows that the transverse component is mainly related to
three-dimensional effects. Theoretical findings display a satisfactory agreement with
results of flume experiments. Transverse variations are responsible for the planimetric
instability of the channel; we find that in the range of values of Shields stress typical
of braided rivers, the incipient bifurcation is enhanced as the width ratio of the
channel increases.
Thermally driven motions in a rotating stratified

fluid: theory and experiment
Authors: PEDLOSKY J. , WHITEHEAD J. A. , VEITCH GRAHAM
Published: July 2002

A radial temperature distribution is applied to the top of a cylinder

of rotating stably

stratified fluid. Thermal wind shear drives the interior flow. Linearized
theory

predicts,

and laboratory experiments confirm, that when the stratification is large
enough it

completely suppresses the Ekman pumping into the interior. The interior

velocity field,

which is primarily azimuthal, responds by satisfying the no-slip boundary
conditions

without the need of Ekman layers on the horizontal surfaces. Moreover,
for large

stratification a thermal boundary layer beneath the top surface traps the
thermal

disturbance applied at the upper surface. The greatest azimuthal velocity

occurs at the

base of this layer. Below this layer the azimuthal velocity viscously

diffuses downward

with thermal wind adjusting the temperature. The Rossby radius of deformation
based

on this layer depth is the cylinder's radius divided by the square

root of the Prandtl

number. Detailed measurements of the velocity field generated in the

cylinder by the

heating are compared with the theory in the case where the Ekman layers
are

eliminated by stratification. The theory and experiments agree

qualitatively well over

a range of four orders of magnitude of imposed parameters and over a large
parameter

range the quantitative comparison is also very good.
A frictional–kinetic model for the flow of

granular materials through a wedge-shaped hopper
Authors: JYOTSNA R. , KESAVA RAO K.
Published: July 2002

A quasi-one-dimensional model is used to examine the steady flow
of granular

materials through a wedge-shaped hopper with smooth, steep walls. Hybrid

frictional–kinetic equations are used in an attempt

to overcome some of the dificulties faced

by earlier works, which were based on frictional equations. Owing to computational

difficulties, two different solution procedures are used:

(i) in the upper region, where

frictional effects dominate, and (ii) the lower region which includes

the exit slot and

a part of the particle jet below the hopper, where kinetic and frictional
effects are

expected to be comparable. The equations are integrated numerically in
(i). In (ii),

they are linearized, and a semi-analytical solution is constructed.

In contrast to the

works of Kaza & Jackson (1982a) and Prakash & Rao

(1991), the density varies

smoothly across the exit slot. The density profile is qualitatively

similar to the data

of Fickie, Mehrabi & Jackson (1989). However, the range of density
variation is

much smaller than that observed. Owing to the approximations used, and
perhaps

also to the form of the kinetic constitutive equations, kinetic effects

are dominated by

frictional effects, except close to the downstream boundary.
Three-dimensional instability of viscoelastic elliptic vortices
Authors: HAJ-HARIRI H. , HOMSY G. M.
Published: July 2002

An analysis of the three-dimensional instability of two-dimensional

viscoelastic elliptical flows is presented, extending the inviscid analysis

of Bayly (1986) to include

both viscous and elastic effects. The problem is governed by three parameters:

E, a geometric parameter related to the ellipticity; Re,

a wavenumber-based Reynolds

number; and De, the Deborah number based on the period of the
base

flow. New modes and mechanisms of instability are discovered. The flow

is generally susceptible

to instabilities in the form of propagating plane waves with a rotating
wavevector,

the tip of which traces an ellipse of the same eccentricity as the flow,

but with the

major and minor axes interchanged. Whereas a necessary condition for purely
inertial

instability is that the wavevector has a non-vanishing component along
the vortex

axis, the viscoelastic modes of instability are most prominent when their
wavevectors

do vanish along this axis. Our analytical and numerical results delineate
the region

of parameter space of (E, ReDe) for which

the new instability exists. A simple model

oscillator equation of the Mathieu type is developed and shown to embody
the

essential qualitative and quantitative features of the secular

viscoelastic instability.

The cause of the instability is a buckling of the ‘compressed’

polymers as they are

perturbed transversely during a particular phase of the passage of the
rotating plane

wave.
Torsional flow: effect of second normal stress
difference on elastic instability in a finite domain
Authors: AVAGLIANO AARON , PHAN-THIEN NHAN
Published: July 2002

A rotational shear flow is examined in the bounded parallel-plate
geometry for a
four-constant Oldroyd-type fluid which has a constant viscosity, and constant
first
and second normal stress coefficients. A new type of Galerkin spectral
technique
is introduced to solve the resulting two-dimensional stiff boundary value
problem.
We show that even a small second normal stress difference can lead to a
significant
increase (nearly 100%) in the stability of the base torsional flow. Beyond
a critical
Deborah number the secondary flow, in the form of travelling waves, appears
to be
confined between two critical radii, in qualitative agreement with the
experimental
results of Byars et al. (1994). The mechanism behind this instability
is investigated
for dilute polymer solutions.
Unsteady convective exchange flows in cavities
Authors: STURMAN J. J. , IVEY G. N.
Published: July 2002

Horizontal exchange flows driven by spatial variation of buoyancy
fluxes through the
water surface are found in a variety of geophysical situations. In all
examples of such
flows the timescale characterizing the variability of the buoyancy fluxes
is important
and it can vary greatly in magnitude. In this laboratory study we focus
on the effects
of this unsteadiness of the buoyancy forcing and its influence on the resulting
flushing
and circulation processes in a cavity. The experiments described all start
with
destabilizing forcing of the flows, but the buoyancy fluxes are switched
to stabilizing
forcing at three different times spanning the major timescales characterizing
the
resulting cavity-scale flows. For destabilizing forcing, these timescales
are the flushing
time of the region of forcing, and the filling-box timescale, the time
for the cavity-scale
flow to reach steady state. When the forcing is stabilizing, the major
timescale is the
time for the fluid in the exchange flow to pass once through the forcing
boundary layer.
This too is a measure of the time to reach steady state, but it is generally
distinct from
the filling-box time. When a switch is made from destabilizing to stabilizing
buoyancy
flux, inertia is important and affects the approach to steady state of
the subsequent
flow. Velocities of the discharges from the end regions, whether forced
in destabilizing
or stabilizing ways, scaled as
u∼(Bl)1/3 (where B is
the forcing buoyancy flux and l is
the length of the forcing region) in accordance with Phillips' (1966)
results. Discharges
with destabilizing and stabilizing forcing were, respectively,
Q−∼(Bl)1/3H
and
Q+∼(Bl)1/3δ
(where H is the depth below or above the forcing plate and δ
is the boundary
layer thickness). Thus
Q−/Q+>O(1)

provided H>O(δ), as was certainly the case in

the experiments reported, demonstrating the overall importance of the flushing

processes occurring during periods of cooling or destabilizing forcing.
Fully developed laminar buoyant flow in vertical
cavities and ducts of bounded section
Authors: McBAIN G. D.
Published: July 2002

The fully developed flow in a vertical cavity or duct subject to horizontal heating
is considered. Solutions of the Boussinesq equations are obtained for rectangular
and elliptic sections, in terms of Fourier series and polynomials, respectively. Both
generalize the familiar odd-symmetric cubic profile of the plane cavity. Uniqueness is
demonstrated under the restriction that the flow is independent of height. For cavities
with rectangular sections, it is predicted and verified that the flow in the plane of
spanwise symmetry is practically independent of the span if this exceeds 1.7 times the
breadth.
Mutual Benefit Societies in Argentina:
Workers, Nationality, Social Security and Trade Unionism
Authors: MUNCK RONALDO
Published: July 2002

In the ‘pre-history’ of Argentina's labour movement
lie
the mutual-benefit societies. Although these associations embraced almost
half of the
workers of Buenos Aires at the time of the Centenario (1910) little
is known about
them. The article explores the main parameters shaping the development
of the
mutual benefit societies, their relationship to the immigrant communities
and
their role in relation to social security. It traces, finally, the ambiguous

relationship between the mutual benefit societies and the emergence of
Peronist
trade unionism in the mid-1940s.
Reforming the Nation: Mexican Nationalism in Context
Authors: MORRIS STEPHEN D.
Published: July 2002

With the NAFTA (North American Free Trade Agreement); the
EZLN (Ejército Zapatista de Liberación Nacional),
and political crisis/reform all
posing questions both old and new about Mexican nationalism, this article
reconsiders the dimensions of the subject, the issues, and the empirical evidence.
After setting out an analytical and theoretical framework for the study of
nationalism, it concentrates on the many components of Mexican nationalism, the
historic and on-going nationalist debates over the Indian, the American and the
state, and the nature of nationalist policies over the years. It then reviews
research related to such theoretical issues as the linkages between nationalist
sentiments, ideas and policies, the social bases of nationalist ideas and perceptions,
and the changes in nationalism. The article aims to place longstanding discussions
of Mexican nationalism in a theoretical context and to derive conclusions which
indicate appropriate directions for future research.
Constituencies for reform in Ghana
Authors: Bratton Michael , Lewis Peter , Gyimah-Boadi E
Published: July 2002

The attitudes of ordinary people in Africa towards the liberalisation of politics and economies are not well known. Are there popular constituencies for reform? Which specific reform measures do different social groups accept or reject? And does popular support for structural adjustment, if any, go together with support for democracy? In an effort to find answers, this article reports results of a national sample survey in Ghana conducted in July 1999 as part of the Afrobarometer. The survey finds that the constituency for democracy is broader than the constituency for market reform, which is concentrated among educated male elites. In addition, while most Ghanaians are patient with democracy and want to retain this political regime, most Ghanaians are fatigued with adjustment and want the government to ‘change its policies now’. Given this distribution of popular preferences, one can surmise that democracy will be easier to consolidate than a market-based economy.
Cascade of parametric instabilities in
ionospheric heating experiments
Authors: KUO S. P.
Published: July 2002

Two secondary parametric instabilities providing cascade channels for the
Langmuir sidebands of the oscillating two-stream instability (OTSI) and parametric
decay instability (PDI), which are excited by O-mode high-frequency (HF) heating
waves, are studied. The first one decays a Langmuir pump wave into a Langmuir
sideband and an ion acoustic decay mode. Both resonant and nonresonant cascade
processes are considered. Nonresonant cascade of Langmuir waves proceeds
at the same location and is increasingly hampered by the frequency mismatch effect.
Resonant cascade takes place in different resonant locations to minimize the
frequency mismatch effect, but it has to overcome the severe propagation loss of the
mother Langmuir wave in each cascade step. This process produces a narrow spectrum
of frequency-downshifted (from the HP wave frequency) plasma waves. The
second employs the lower-hybrid wave as the decay mode. Only the nonresonant
cascade is of interest, because the propagation loss of the mother Langmuir wave
in each resonant cascade step is far too severe. This is a three-dimensional coupling
process, because the wavevectors of coupled three waves have to be matched in
three-dimensional space, rather than matched in the conventional way on the plane
of the pump wavevector and the geomagnetic field. A broad spectrum of frequency-downshifted
plasma waves can be produced by this process in a narrow altitude
range preferentially located near the matching heights of Langmuir sidebands of
the OTSI and PDI.
Hydrodynamical equation for electron swarms
Authors: LEBOWITZ JOEL L. , ROKHLENKO A.
Published: July 2002

We study the long-time behaviour of light particles, for example
an electron swarm
in which Coulomb interactions are unimportant, subjected to an external
field and
elastic collisions with an inert neutral gas. The time evolution of the
velocity and
position distribution function is described by a linear Boltzmann equation
(LBE).
The small ratio of electron to neutral masses, ε, makes the energy
transfer between
them very inefficient. We show that, under suitable scalings, the LBE reduces,
in
the limit ε→0, to a formally exact equation for the speed (energy)
and position
distribution of the electrons that contains mixed spatial and speed derivatives.
When
the system is spatially homogeneous, this equation reduces to and thus
justifies,
for small-enough ε, the commonly used ‘two-term’ approximation.
Reproductive biology of spider crab females (Maja brachydactyla) off the coast of Asturias (north-west Spain)
Authors: García-Flórez L. , Fernández-Rueda P.
Published: July 2002

The first results of the females reproductive cycle of Maja brachydactyla (Braquiura: Majidae) off the coast of Asturias (north-west Spain) are presented. Mean size of mature females was 133·4 mm (N=1022) in 1997 and 125·0 mm (N=942) in 1998. Only one cohort is exploited each fishing season. This cohort passed through the terminal moult the year before and recruited in to the fishery beginning in June. The breeding cycle off the coast of Asturias begins in December and ends in November the following year. Results from this study indicate that females produce 3–4 broods per year in these waters, which is the highest reported number for M. brachydactyla. The results are discussed in terms of their importance for management of the fishery.
A new species, Callianassa poorei sp. nov. (Decapoda: Crustacea: Callianassidae) from Tasmania
Authors: Sakai K.
Published: July 2002

As part of my ongoing studies of the Callianassidae, Dr G. Poore of the Museum of Victoria, Australia, sent me four small specimens from Tasmania. These specimens, which include two ovigerous females, are closely allied to Callianassa lewtonae from the northern Great Barrier Reef, Queensland, Australia. They differ from that species because the merus of the chelipeds bears a triangular ventral lobe in the larger cheliped and a sharp ventral spine in the smaller cheliped; and the antennular peduncle is much longer than the antennal peduncle. Only Callianassa ceramica, C. arenosa, and C. australiensis have been previously recorded from Tasmanian waters.

Abbreviations used are: MV, Museum of Victoria, Australia; CL, carapace length; TL, whole length of the specimen from the tip of rostrum to the end of telson; A1, antennule; A2, antenna; P, pereiopod; Plp, pleopod.
Evidence of a sexual pause in Bathymodiolus azoricus (Bivalvia: Mytilidae) from hydrothermal vents of the Mid-Atlantic Ridge
Authors: Comtet Thierry , Le Pennec Marcel , Desbruyères Daniel
Published: July 2002

Histological sections of the gonad of Bathymodiolus azoricus from the Lucky Strike and Menez Gwen hydrothermal vent fields (Mid-Atlantic Ridge) demonstrated a spawning event in this species in May 1994, synchronous between the two vent fields located 60 km apart, and a sexual pause in gametogenesis. As reported for other vent mytilid species, B. azoricus from Lucky Strike and Menez Gwen could exhibit hermaphroditism.
Malnutrition and parasitic helminth infections
Authors: STEPHENSON L.S. , LATHAM M.C. , OTTESEN E.A.
Published: July 2002

The Global Burden of Disease caused by the 3 major intestinal nematodes is an estimated 22·1million disability-adjusted life-years (DALYs) lost for hookworm, 10·5million for Ascaris lumbricoides, 6·4million for Trichuris trichiura, and 39·0million for the three infections combined (as compared with malaria at 35·7million) (World Bank, 1993; Chan et al. 1994); these figures illustrate why some scarce health care resources must be used for their control. Strongyloides stercoralis is the fourth most important intestinal worm infection; its nutritional implications are discussed, and the fact that its geographic distribution needs further study is emphasized. Mechanisms underlying the malnutrition induced by intestinal helminths are described. Anorexia, which can decrease intake of all nutrients in tropical populations on marginal diets, is likely to be the most important in terms of magnitude and the probable major mechanism by which intestinal nematodes inhibit growth and development. We present a revised and expanded conceptual framework for how parasites cause/aggravate malnutrition and retard development in endemic areas. Specific negative effects that a wide variety of parasites may have on gastrointestinal physiology are presented. The synergism between Trichuris and Campylobacter, intestinal inflammation and growth failure, and new studies showing that hookworm inhibits growth and promotes anaemia in preschool (as well as school-age) children are presented. We conclude by presenting rationales and evidence to justify ensuring the widest possible coverage for preschool-age children and girls and women of childbearing age in intestinal parasite control programmes, in order to prevent morbidity and mortality in general and specifically to help decrease the vicious intergenerational cycle of growth failure (of low-birth-weight/intrauterine growth retardation and stunting) that entraps infants, children and girls and women of reproductive age in developing areas.
Cuticle heterogeneity as exhibited by Pasteuria spore attachment is not linked to the phylogeny of parthenogenetic root-knot nematodes (Meloidogyne spp.)
Authors: DAVIES K.G. , FARGETTE M. , BALLA G. , DAUDI A. , DUPONNOIS R. , GOWEN S.R. , MATEILLE T. , PHILLIPS M.S. , SAWADOGO A. , TRIVINO C. , VOUYOUKALOU E. , TRUDGILL D.L.
Published: July 2002

The cuticle is a major barrier prohibiting the infection of nematodes against micro-organisms. The attachment of bacterial spores of the nematode hyperparasite Pasteuria penetrans (PP1) to field populations of root-knot nematodes (RKN, Meloidogyne spp.) from Burkino Faso, Ecuador, Greece, Malawi, Senegal and Trinidad and Tobago were assayed in standard attachment tests. The attachment of spore population PP1 to different field populations of root-knot nematode showed that the rates of attachment differed between countries. Similar tests were also undertaken on P. penetrans spores from these countries against 2 species of RKN, M. incognita and M. arenaria. The results showed a high degree of variability in spore attachment with no clear distinction between the 2 species of nematode. It has been hypothesized that Pasteuria spore attachment is linked to nematode species designations and this study clearly shows that this is not the case. Further tests showed that variation in spore attachment was not linked to nematode phylogeny. The results therefore beg the question of how do parthenogenetic root-knot nematodes maintain cuticle variability in the face of such an aggressive hyperparasite.
Landscape features associated with infection by a malaria parasite (Plasmodium mexicanum) and the importance of multiple scale studies
Authors: EISEN R. J. , WRIGHT N. M.
Published: July 2002

In a 3-year study, we examined landscape features (aspect, slope, sun exposure, canopy cover, type of ground cover, and nearest water source) that were potentially related to prevalence of infection withPlasmodium mexicanumin fence lizards (Sceloporus occidentalis) within a 4.5 ha study area in northern California, USA. Logistic regression analysis showed that ground cover type was the primary mediator of the probability ofP. mexicanuminfection. Infected lizards were captured more often in rock and/or leaf litter locations than in grassy ones. In another experiment, the study area was divided into 9 sites (0.07–0.33 ha), and infection prevalence was calculated for each. Three sites with high (>30%) infection prevalence had significantly more rocky outcrops and leaf litter than those with low (<20%) or moderate (20–30%) infection prevalence (N= 3 sites each). We conclude that lizard site selection may influence the probability of exposure to infected vectors and thus the likelihood ofP. mexicanuminfection. We also demonstrate that studies at different spatial scales may be required to understand fully the relationship between landscape features and parasite distribution.
The effects of the peptides AF3 (AVPGVLRFamide) and
AF4 (GDVPGVLRFamide) on the somatic muscle of the
parasitic nematodes Ascaris suum and Ascaridia galli
Authors: TRIM N. , HOLDEN-DYE L. , RUDDELL R. , WALKER R. J.
Published: July 2002

AF3 (AVPGVLRFamide) and AF4 (GDVPGVLRFamide) are endogenous RFamide-like
peptides isolated from the
parasitic nematode Ascaris suum. Here the actions of these peptides
on the somatic musculature of Ascaris have been
investigated and compared to the action of acetylcholine (ACh), the
excitatory transmitter at the neuromuscular junction.
ACh, AF3 and AF4 contracted muscle with EC50s of
13±1 μM, 24±6 nM and 37±2 nM,
respectively (n=6). The muscle
cells were depolarized by ACh (3 μM; 5·2±0·4
mV,
n=42), AF3 (1 μM; 2·6±0·3 mV,
n=19) and AF4 (1 μM;
3·3±0·4 mV, n=19). EC50s were
681±329 nM (AF3) and 901±229 nM (AF4),
but an
estimate could not be made for ACh
due to muscle contraction at concentrations greater than 10 μM.
The
depolarization to 3 μM ACh was abolished by the
nicotinic receptor antagonist mecamylamine (10 μM;
n=5) but the responses to the peptides were not (111±7%
and
108±17% with respect to control; n=5). The depolarization
elicited by ACh was reduced to a greater extent by a 50%
reduction in extracellular Na+
concentration than the response to AF3 and AF4 (P<0·02).
Cobalt was more effective at
blocking the AF3 and AF4 depolarizations than those to ACh. These
observations suggest that AF3 and AF4 contract
Ascaris muscle without an action at the Ascaris nicotinic
receptor. Furthermore, the ionic mechanism through which AF3
and AF4 depolarize Ascaris muscle is different from that for ACh.
ACh,
AF3 and AF4 were also found to contract Ascaridia
galli somatic muscle with EC50s of 13±3 μM,
721±236 nM and 371±177 nM, respectively
(n=7). The muscle cells were
depolarized by ACh (EC50=14±5 μM, n=5),
AF3 (EC50=5±3 μM, n=4) and AF4
(EC50=10±5 μM, n=4). Therefore the
response
to these peptides is not unique to Ascaris and they may subserve
a
functional role in the motor nervous system of parasitic nematodes.
Modulation of enzymatic activity of Src-family kinases in
bovine T cells transformed by Theileria parva
Authors: FICH C. , KLAUENBERG U. , FLEISCHER B. , BRÖKER B. M.
Published: July 2002

After infection with sporozoites of the protozoon Theileria
parva
(Tp) bovine T cells are readily transformed to permanent
growth in vivo and in vitro. Their transformed state

depends on the constant presence of the parasite but membrane signals
remain important. Non-receptor tyrosine kinases play a critical role in

the transduction of membrane signals in haematopoietic cells.
We have investigated Src-family kinases in bovine T cells transformed by

Tp. The T cell receptor-associated tyrosine kinase p60fyn

had high activity in all cell lines tested. In addition, weak phosphorylation

of 2 novel bands was
observed associated with Fyn. In contrast to Fyn, enzymatic activity of

p56lck, which in T cells has an essential role in
signalling, was low. Furthermore, 1 of 3 Tp transformed cell
lines was completely devoid of p56lck indicating that
the
enzyme is not necessary for the Tp dependent growth of the T cells.
In addition to
p60fyn and p56lck weak enzymatic

activity of 1 splice variant of p53/56lyn
was observed after infection of T cells with Tp. These data show
that growth
transformation by Tp influences kinase activity in bovine T cells. However,

they also prove that p56lck does not play an
essential role in the transformation mechanism.
The evolution of immunoassay technology
Authors: RONALD A. , STIMSON W. H.
Published: July 2002

Since they were first utilized, immunoassays have witnessed phenomenal growth in the range and scope of their
applications. A vast array of different labels and assay strategies has been developed to meet the requirements of sensitivity,
accuracy and convenience. The development of increasingly sensitive labels and detection equipment has seen a drastic
improvement in the sensitivity of immunoassay systems, allowing an ever-increasing range of analytes to be measured
accurately. At the same time, simple to use, inexpensive assay systems have been developed with the necessary reliability,
accuracy and sensitivity to bring immunoassay technology to much more diverse areas such as home testing, near-patient
monitoring, and large screening programmes in developing countries. Recent developments in molecular biology techniques
have made possible the production of fusion antibody conjugates, which can lead to further improvements in
sensitivity and cost of reagents, as well as possibly revolutionizing the production of monoclonal antibodies. However,
dissatisfaction with various aspects of existing immunoassay technology will necessarily lead to the continued development
of this already widely diverse subject.
The origin and function of cement gland secretion in
Pomphorhynchus laevis (Acanthocephala)
Authors: DEZFULI B. S. , CAPUANO S. , PIRONI F. , MISCHIATI C.
Published: July 2002

Cement gland protein in male and inseminated female individuals of an acanthocephalan parasite of fish, Pomphorhynchus
laevis (Müller, 1776), was localized by immunohistochemistry using an antibody specific for cement protein. Male P. laevis
possess 3 pairs of round to oval cement glands ranging from 0·5 to 0·9 mm in length and from 0·3 to 0·7 mm in width. Each
gland has an outer portion containing nuclear fragments and other cellular organelles surrounding a space for storage of
gland products. Very little work has been carried out on the nature of the cement gland secretions. We have previously
reported that the major component of cement is a protein with molecular weight of 23 kDa; in fresh glands it is white in
colour. Immunohistochemical studies herein reported were carried out using a polyclonal antibody raised against purified
P. laevis p23 cement protein (anti-p23PL). Localization of p23 cement protein at the light microscope level, by means of
the anti-p23PL antibody, shows that p23 is present within the cytoplasmic layer of the gland as well as in the gland duct
lumen. Interestingly, the p23 cement protein was also identifiable at the posterior ends of females retaining the cap.
Positivity to anti-p23PL antibody was obtained not only in the external part of the copulatory cap, but also within the
vaginal tract and at the base of the uterine duct. Thus, we report herein the first photographic evidence that the copulatory
cap is not a simple gonopore lid but it is really an intravaginal plug.
Impaired generation and use of strategy in schizophrenia: evidence
from
visuospatial and verbal tasks
Authors: IDDON J. L. , McKENNA P. J. , SAHAKIAN B. J. , ROBBINS T. W.
Published: July 2002

Background. The aim of this study was to investigate mnemonic

strategic deficits in schizophrenic patients.

Methods. Analogous tasks were used that required the self-generation

of an efficient strategy and
its implementation in two domains: visuospatial and verbal. The tasks were
given to 20 IQ
preserved schizophrenics and 20 matched normal controls. A number of
different scores was derived
from each task including strategy, short-term memory capacity and perseveration.

Results. Overall, the schizophrenic patients were significantly

impaired in their ability to generate
effective mnemonic strategies on both tasks. In addition, on the visuospatial
task there was no
difference between the groups on the memory scores, but the schizophrenic
patients made
significantly more perseverative errors than controls. They were disproportionately
worse on the
verbal strategy task, showing impairment on memory as well as on strategy
scores and were also
impaired at semantically classifying the words. Performance was similar
to the deficit seen in
patients with frontal lobe excisions and Parkinson's disease,
in terms of the inability to generate an
effective strategy. The deficit on the verbal task was similar
to patients with temporal lobe excisions
who show impaired verbal memory. However, the pattern differed in the sense
that the temporal
lobe patients were able to generate effective strategies, unlike the patients

with schizophrenia.

Conclusions. High functioning schizophrenic patients are impaired

in utilizing visuospatial and
verbal mnemonic strategies. By comparing the results with those of
neurosurgical excision patients,
further evidence is provided for both frontal and temporal lobe involvement
in schizophrenia.
Predictors of change in anxiety symptoms of older
persons: results from the Longitudinal Aging Study
Amsterdam
Authors: DE BEURS E. , BEEKMAN A. T. F. , DEEG D. J. H. , VAN DYCK R. , VAN TILBURG W.
Published: July 2002

Background. Data on the course of anxiety in late life are scarce. The present study sets out to
investigate the course of anxiety, as measured by the HADS-A (Zigmond & Snaith, 1983) in
community dwelling older persons, and to evaluate predictive factors for change over 3 years in
anxiety symptoms following the vulnerability/stress model.

Method. Based on the first anxiety assessment, two cohorts were formed: subjects with and subjects
without anxiety symptoms. In the non-anxious cohort (N = 1602) we studied risk factors for the
development of anxiety symptoms; in the anxious cohort (N = 563) the same factors were evaluated
on their predictive value for restitution of symptoms. Risk factors included vulnerability factors
(demographics, health status, personality characteristics and social resources) and stressors (life
events occurring in between both anxiety assessments). Logistic regression models estimated the
effects of vulnerability factors, stress and their interaction on the likelihood of becoming anxious
and chronicity of anxiety symptoms.

Results. It was indicated that the best predictors for becoming anxious were being female, high
neuroticism, hearing/eyesight problems and life-events. Female sex and neuroticism also increased
the likelihood of chronicity of anxiety symptoms in older adults, but life events were not related to
chronicity. The main stressful event in late life associated with anxiety was death of one's partner.
Vulnerability factors and stress added on to each other rather than their interaction being associated
with development or chronicity of anxiety.

Conclusion. The vulnerability/stress model offers a useful framework for organizing risk factors for
development and chronicity of anxiety symptoms in older persons, but no support was attained for
the hypothesis that vulnerability and stress amplify each others effects. Finally, the results indicate
to whom preventive efforts should be directed: persons high in neuroticism, women, and those who
experience distressing life events.
Equity in Health Service Use by Children: Examining the
Ethnic Paradox
Authors: COOPER HELEN , SMAJE CHRIS , ARBER SARA
Published: July 2002

This article investigates whether equity is achieved in health service
utilisation by children and young people aged 0–19 years. Data from the
British General Household Survey 1991–4 is used to examine the influence
of ethnicity, along with social class, housing tenure, family structure
and employment of parents on the use of general practitioner, outpatient
and inpatient services. Health status is the most powerful predictor of use
for each health service and there is no evidence of socioeconomic
inequalities. However, a clear ‘ethnic paradox’ persists after controlling
for socioeconomic and demographic factors. South Asian children have a
higher utilisation of GP services than any other ethnic group, but the use
of hospital services is lower for children in all minority ethnic groups
relative to the white population. Possible explanations for this paradox
are examined in relation to indirect indicators of service quality. There is
no evidence to suggest that South Asian children visit the doctor more
frequently for a given illness episode than white children, but having a non-UK-
born mother is associated with increased consultation and reduced use
of outpatient services relative to UK-born South Asian parents.
Susan F. Hirsch, Pronouncing and persevering:
Gender and the discourses of disputing in an African Islamic
court. (Language and legal discourse.) Chicago: University
of Chicago Press, 1998. Pp. xiii, 360. Hb $48.00, pb $19.00.
Authors: Matoesian Gregory M.
Published: July 2002

According to feminist writings, Islamic women lack
agency and power, and are oppressed compared to their Western
female counterparts. A major site of such oppression is
in Islamic courts, where husbands possess authority to
pronounce divorce – while their subordinate wives
humbly accept the decree and persevere, silently enduring
the hardships that result. In stark contrast to such stereotypic
images of gender relations in Islamic societies, Hirsch's
beautifully written and powerful book focuses on the discursive
production and reproduction of gender in Swahili Muslim
courts. In so doing, it offers a quite different view of
gender relations in Islamic society. In rich, fine-grained
linguistic detail, Hirsch analyzes how legal processes
in divorce cases not only reproduce but also undermine
and transform dominant cultural images of gender.
Nirmala Srirekam PuruShotam, Negotiating language,
constructing race: Disciplining difference in Singapore.
(Contributions to the sociology of language, 79.) Berlin:
Mouton de Gruyter, 1998. Pp. viii, 294. Hb DM 178.00.
Authors: Gupta Anthea Fraser
Published: July 2002

Singapore has been much discussed as a highly developed,
multilingual, multicultural city-state with a clearly articulated
language policy, implemented by a strong government as
part of its efforts at social engineering. Singapore's
policies are variously derided and praised. Some of those
who have written on the sociology of language in Singapore
have reiterated government policy with little or no assessment
of its meaning; thus one regularly reads that all children
in Singapore receive education in English and in their
mother tongue – a statement that cannot be understood
without a grasp of what the concept “mother tongue”
means in Singapore's socio-political system. PuruShotam's
book comes from a group of scholars who are working with
a theoretically informed perspective on language and ethnicity,
which questions terminologies and seeks to understand how
notions like “race,” “mother tongue,”
and “language” work as social constructs. In
Singapore this approach has been especially associated
with the sociologists Geoffrey Benjamin, Sharon Siddique,
Chua Beng Huat, and PuruShotam herself.
Robert J. Baumgardner (ed.), South Asian English:
Structure, use, and users. (English in the global
context.) Urbana: University of Illinois Press, 1996. Pp.
xx, 286. Hb $44.95, pb $16.95.
Authors: Gair James W.
Published: July 2002

Fifty years after the nations of South Asia gained
their independence from Britain, the language of the colonialists
remains very much alive in the region. In fact, in some
respects it is even more alive than at the time of departure
– as witnessed by the efflorescence of South Asian
writers in English of international stature, to the extent
that the New Yorker has devoted the major part
of an issue to them (June 23–30, 1997).
Phylogenetic data bearing on the REM sleep learning connection
Authors: Siegel J. M.
Published: July 2002

The phylogenetic data are inconsistent with the hypothesis that REM sleep duration is correlated with learning or learning ability. Humans do not have uniquely high amounts of REM sleep. The platypus, marsupials, and other mammals not generally thought to have extraordinary learning abilities have the largest amounts of REM sleep. The whales and dolphins (cetaceans) have the lowest amounts of REM sleep and may go without REM sleep for extended periods of time, despite their prodigious learning abilities.

Vertes & Eastman]
How smart can simple heuristics be?
Authors: Chater Nick
Published: July 2002

This commentary focuses on three issues raised by Gigerenzer, Todd, and the ABC Research Group (1999). First, I stress the need for further experimental evidence to determine which heuristics people use in cognitive judgment tasks. Second, I question the scope of cognitive models based on simple heuristics, arguing that many aspects of cognition are too sophisticated to be modeled in this way. Third, I note the complementary role that rational explanation can play to Gigenerenzer et al.'s “ecological” analysis of why heuristics succeed.
Simple heuristics could make us smart; but which heuristics do we apply when?
Authors: Cooper Richard
Published: July 2002

Simple heuristics are clearly powerful tools for making near optimal decisions, but evidence for their use in specific situations is weak. Gigerenzer et al. (1999) suggest a range of heuristics, but fail to address the question of which environmental or task cues might prompt the use of any specific heuristic. This failure compromises the falsifiability of the fast and frugal approach.
Against an uncritical sense of adaptiveness
Authors: Fuller Steve
Published: July 2002

The “adaptive toolbox” model of the mind is much too uncritical, even as a model of bounded rationality. There is no place for a “meta-rationality” that questions the shape of the decision-making environments themselves. Thus, using the ABC Group's “fast and frugal heuristics,” one could justify all sorts of conformist behavior as rational. Telling in this regard is their appeal to the philosophical distinction between coherence and correspondence theories of truth.
Iterative processing of information during sleep may improve consolidation
Authors: Cipolli Carlo
Published: July 2002

The relationship between sleep and memory has been controversial since the 1950s. Studies on delayed dream recall and long-term retention of pre-sleep stimuli indicate that sleep may have a positive role in the consolidation of information. This positive indication counterbalances the negative one from the studies on the effects of REM deprivation.

[Vertes & Eastman]
The Law of Practice and localist neural network models
Authors: Heathcote Andrew , Brown Scott
Published: July 2002

An extensive survey by Heathcote et al. (in press) found that the Law of Practice is closer to an exponential than a power form. We show that this result is hard to obtain for models using leaky competitive units when practice affects only the input, but that it can be accommodated when practice affects shunting self-excitation.
On the meaning and function of normative analysis: Conceptual blur in the rationality debate?
Authors: Mandel David R.
Published: July 2002

The rationality debate centers on the meaning of deviations of decision makers' responses from the predictions/prescriptions of normative models. But for the debate to have significance, the meaning and functions of normative analysis must be clear. Presently, they are not, and the debate's persistence owes much to conceptual blur. An attempt is made here to clarify the concept of normative analysis.
The dramaturgy of dreams in Pleistocene minds and our own
Authors: Gunderson Keith
Published: July 2002

The notion of simulation in dreaming of threat recognition and avoidance faces difficulties deriving from (1) some typical characteristics of dream artifacts (some “surreal,” some not) and (2) metaphysical issues involving the need for some representation in the theory of a perspective subject making use of the artifact.

[Hobson et al.; Revonsuo]
Consciousness and mental representation
Authors: Gilman Daniel
Published: July 2002

Block (1995t) has argued for a noncognitive and non-
representational notion of phenomenal consciousness, but his putative
examples of this phenomenon are conspicuous in their representational
and functional properties while they do not clearly possess other
phenomenal properties.
A reader's point of view on looking
Authors: Fischer Martin H.
Published: July 2002

Questions about the validity of eye fixations in the blocks task as a memory indicator are discussed. Examples from reading research illustrate the influence of extraneous factors.