bluuebunny/crossref_metadata_2025 huggingface dataset:
Rotation and nitrogen fertilizer effects on pearl millet,
cowpea and groundnut yield and soil chemical
properties in a sandy soil in the semi-arid tropics,
West Africa
Authors: BATIONO A. , NTARE B. R.
Published: July 2002

A 5-year study was conducted from 1988 to 1992 at three sites in Niger to determine the effects of
crop rotation of a cereal and legumes and nitrogen fertilizer on chemical properties of the soil
(0–20 cm) and yield of pearl millet (Pennisetum glaucum (L.) R.BR.), cowpea (Vigna unguiculata (L.)
Walp.), and groundnut (Arachis hypogea L.). Four N levels and rotation treatments including
continuous fallow were investigated. Soil samples taken from the top 20 cm depth at the end of the
experiment from treatments without nitrogen application which included continuous fallow,
fallow–millet rotation, groundnut–millet rotation, cowpea–millet rotation, and continuous millet
were analysed for soil pH, organic carbon, total nitrogen and exchangeable bases. Fertilizer N
significantly increased yield of pearl millet, cowpea and groundnut. Continuous monocropping of
pearl millet resulted in lower yields across N levels compared to legume–millet rotations. Legume
yields were also consistently lower in monoculture than when rotated with millet. There was a decline
in organic matter under continuous millet, cowpea–millet rotation and groundnut–millet rotation.
The fallow–millet rotation supplied more mineral N than the legume–millet rotations. Nitrogen
availability was greater in cowpea–millet rotation than continuous millet. Crop rotation was more
productive than the continuous monoculture but did not differ in maintaining soil organic matter.
The legume–millet rotation at 30 kg/ha N appears to be the most viable for millet production.
Research should focus on understanding the effect of legume/cereal intercrops and rotations on soil
productivity.
DETERMINANTS OF USE OF MATERNAL–CHILD HEALTH SERVICES IN RURAL GHANA
Authors: ADDAI ISAAC
Published: July 2002

This study uses data from the Ghana Demographic and Health Survey (GDHS) of 1993 to examine factors determining the use of maternal–child health (MCH) services in rural Ghana. The MCH services under study are: (1) use of a doctor for prenatal care; (2) soliciting four or more antenatal check-ups; (3) place of delivery; (4) participation in family planning. Bivariate and multivariate techniques are employed in the analyses. The analyses reveal that the use of MCH services tends to be shaped mostly by level of education, religious background and region of residence, and partially by ethnicity and occupation. The implications of these results are discussed.
THE EFFECT OF BIRTH INTERVAL ON MALNUTRITION IN BANGLADESHI INFANTS AND YOUNG CHILDREN
Authors: MOZUMDER A. B. M. KHORSHED ALAM , KHUDA BARKAT-E- , KANE THOMAS T. , LEVIN ANN , AHMED SHAMEEM
Published: July 2002

This study was undertaken to investigate the independent effect of the length of birth interval on malnutrition in infants, and children aged 6–39 months. Data for this study were drawn from a post-flood survey conducted during October–December 1988 at Sirajganj of the Sirajgani district and at Gopalpur of the Tangail district in Bangladesh. The survey recorded the individual weights of 1887 children. Cross-tabulations and logistic regression procedures were applied to analyse the data. The proportion of children whose weight-for-age was below 70% (moderate-to-severely malnourished) and 60% (severely malnourished) of the NCHS median was tabulated against various durations of previous and subsequent birth intervals. The odds of being moderately or severely malnourished were computed for various birth intervals, controlling for: the number of older surviving siblings; maternal education and age; housing area (a proxy for wealth); age and sex of the index child; and the prevalence of diarrhoea in the previous 2 weeks for the index child.

About one-third of infants and young children were moderately malnourished and 15% were severely malnourished. The proportion of children who were under 60% weight-for-age decreased with the increase in the length of the subsequent birth interval, maternal education and housing area. The proportion of malnourished children increased with the number of older surviving children. Children were at higher risk of malnutrition if they were female, their mothers were less educated, they had several siblings, and either previous or subsequent siblings were born within 24 months. This study indicates the potential importance of longer birth intervals in reducing malnutrition in children.
URINARY SCHISTOSOMIASIS AMONG SCHOOL CHILDREN IN NIGERIA: CONSEQUENCES OF
INDIGENOUS BELIEFS AND WATER CONTACT ACTIVITIES
Authors: AMAZIGO U. O. , ANAGO-AMANZE C. I. , OKEIBUNOR J. C.
Published: July 2002

A study of urinary schistosomiasis in Umueze-Anam, Anambra State,
Nigeria, showed a Schistosoma haematobium infection of 26% (85) among school
children with no significant difference by sex except when age as a variable
is introduced. Eleven percent (37) of the 333 children were positive for
haematuria; all these 37 children lived within 1·0 km of the water sources. Of
the 85 infected children, swimming and laundering accounted for 65% and 48% of
all water contact activities, for boys and girls respectively. One-third of
the 230 adults interviewed believed haematuria to be a venereal disease and
20% thought it was a sign of maturity. Individual perception of causation and
seriousness of haematuria differed by level of education and by sex. Less than
2% of the
respondents knew that snails
transmitted the disease. The effects of social restrictions on the
epidemiology of infection is discussed.
INFANT FEEDING PRACTICES AND CHILD HEALTH IN BOLIVIA
Authors: FORSTE RENATA
Published: July 2002

The effects of breast-feeding and supplementation practices on recent diarrhoea occurrence and stunted growth are modelled using logistic regression techniques. Data from the Demographic and Health Survey of Bolivia, 1989, show that, among children aged 3-36 months at the date of interview, the benefits of breast-feeding to child health were most pronounced among children living in rural poverty. Reduced breast-feeding among these children increased the likelihood of diarrhoea and stunted growth. In addition, the introduction of solid foods to currently lactating infants negatively influenced child health.
Study on the relationship between milk immune factors and
Staphylococcus aureus intramammary infections in dairy cows
Authors: PICCININI RENATA , BRONZO VALERIO , MORONI PAOLO , LUZZAGO CAMILLA , ZECCONI ALFONSO
Published: July 2002

The distribution of Staphylococcus aureus within herds seems to be related
to interactions among the shedding characteristics of the bacteria, their pathogenicity
and mammary gland immune status. The aim of the present study was to
investigate the relationships between selected mammary gland immune factors and
intramammary infections associated with Staph. aureus. Overall, 70 cows from five
commercial dairy herds were included in the study and quarter milk samples were
assessed using bacteriological and cytological tests. We evaluated differential cell
count, lysozyme concentration, N-acetyl-β-glucosaminidase (NAGase) activity, cell
viability and respiratory burst activity in randomly chosen quarter milk samples
from each cow. Staph. aureus intramammary infection elicited different responses in
the mammary gland immune defences investigated. Polymorphonuclear leucocytes
(PMN) as a proportion of total somatic cells in milk, cell viability and NAGase
activity were higher in infected quarters, while the proportions of macrophages and
lymphocytes, respiratory burst activity and lysozyme levels were lower. Mean values
differed among herds, but the differences were not significant. These changes were
associated with Staph. aureus infection. The reduced respiratory burst activity
together with the increase in the proportion of PMN suggests that both the number
and activity of PMN could influence the susceptibility of the mammary gland to
pathogens. Indeed, the logistic model adopted suggests that impairment of milk
immune factors could be concurrent with the development of an infection.
Streamwise oscillations of a cylinder in steady current.
Part 2. Free-surface effects on vortex formation and loading
Authors: CETINER O. , ROCKWELL D.
Published: July 2002

A cylinder in a steady current beneath a free surface is subjected to oscillations in the
streamwise direction. Techniques of high-image-density particle image velocimetry and
instantaneous force measurement provide the relationship between the instantaneous,
global flow patterns and the unsteady loading on the cylinder.

The existence of locked-on states for the fully submerged cylinder is addressed
in the companion study of Cetiner & Rockwell (2001). The present investigation
shows that it is possible to generate distinctly different locked-on states of vortex
formation, provided the cylinder is located immediately beneath the free surface. As
a consequence, the time-dependent transverse force is phase-locked to the cylinder
motion. In the event that a finite gap exists between the cylinder and the free surface,
however, instantaneous, jet-like flow through the gap acts to destabilize such locked-on
states. Lissajous representations of the forces demonstrate the degree of phase-locking
or, in some cases, a loss of lock-on and associated phase drift. Moreover, the degree of
submergence of the cylinder beneath the free surface has remarkable consequences for
the magnitudes of positive and negative spikes of the time-dependent force signatures,
as well as the averaged spectra of the transverse force. In turn, these alterations of the
unsteady transverse force are accompanied by substantial changes of the averaged
in-line and transverse forces.

Vortex systems can exist at locations both upstream and downstream of the cylinder.
They are due to vorticity from the cylinder surface and/or the free surface. The space–time
development of the entire system of vorticity concentrations is interpreted in
terms of the time histories of the relative velocity of the cylinder and the instantaneous
forces on the cylinder. In turn, these features of the vorticity field are related to critical
points near the free surface, deduced from topologies of the corresponding velocity
and streamline patterns. Despite the fact that changes in the patterns of vorticity
and the corresponding topologies occur in conjunction with large fluctuations of the
transverse force coefficient, the dimensionless strength of the vortices is below the
threshold for which distinguishable, localized deformations of the free surface occur.
Large-eddy simulation of boundary-layer separation and transition at a change of surface curvature
Authors: YANG ZHIYIN , VOKE PETER R.
Published: July 2002

Transition arising from a separated region of flow is quite common and plays an
important role in engineering. It is difficult to predict using conventional models
and the transition mechanism is still not fully understood. We report the results of
a numerical simulation to study the physics of separated boundary-layer transition
induced by a change of curvature of the surface. The geometry is a flat plate with a
semicircular leading edge. The Reynolds number based on the uniform inlet velocity
and the leading-edge diameter is 3450. The simulated mean and turbulence quantities
compare well with the available experimental data.

The numerical data have been comprehensively analysed to elucidate the entire
transition process leading to breakdown to turbulence. It is evident from the simulation
that the primary two-dimensional instability originates from the free shear in
the bubble as the free shear layer is inviscidly unstable via the Kelvin–Helmholtz
mechanism. These initial two-dimensional instability waves grow downstream with
a amplification rate usually larger than that of Tollmien–Schlichting waves. Three-dimensional
motions start to develop slowly under any small spanwise disturbance
via a secondary instability mechanism associated with distortion of two-dimensional
spanwise vortices and the formation of a spanwise peak–valley wave structure. Further
downstream the distorted spanwise two-dimensional vortices roll up, leading
to streamwise vorticity formation. Significant growth of three-dimensional motions
occurs at about half the mean bubble length with hairpin vortices appearing at this
stage, leading eventually to full breakdown to turbulence around the mean reattachment
point. Vortex shedding from the separated shear layer is also observed and
the ‘instantaneous reattachment’ position moves over a distance up to 50% of the
mean reattachment length. Following reattachment, a turbulent boundary layer is
established very quickly, but it is different from an equilibrium boundary layer.
The dynamics of a swirling flow in a pipe and

transition to axisymmetric vortex breakdown
Authors: WANG S. , RUSAK Z.
Published: July 2002

This paper provides a new study of the axisymmetric vortex

breakdown phenomenon.

Our approach is based on a thorough investigation of the axisymmetric unsteady

Euler equations which describe the dynamics of a swirling flow in a finite-length

constant-area pipe. We study the stability characteristics as well as

the time-asymptotic

behaviour of the flow as it relates to the steady-state solutions. The
results are

established through a rigorous mathematical analysis and provide a solid
theoretical

understanding of the dynamics of an axisymmetric swirling flow. The stability
and

steady-state analyses suggest a consistent explanation of the mechanism
leading to

the axisymmetric vortex breakdown phenomenon in high-Reynolds-number swirling

flows in a pipe. It is an evolution from an initial columnar swirling flow
to another

relatively stable equilibrium state which represents a flow around a separation
zone.

This evolution is the result of the loss of stability of the base columnar
state when

the swirl ratio of the incoming flow is near or above the critical level.
Theory and experiment on the

low-Reynolds-number expansion and contraction

of a bubble pinned at a submerged tube tip
Authors: WONG HARRIS , RUMSCHITZKI DAVID , MALDARELLI CHARLES
Published: July 2002

The expansion and contraction of a bubble pinned at a

submerged tube tip and driven

by constant gas flow rate Q are studied both

theoretically and experimentally for

Reynolds number Re[Lt ]1. Bubble shape, gas pressure,

surface velocities, and

extrapolated detached bubble volume are determined by a

boundary integral method for various Bond

(Bo=ρga2/σ)

and capillary

(Ca=μQ/σa2)

numbers, where a is the

capillary radius, ρ and μ are the liquid density and

viscosity, σ is the surface tension,

and g is the gravitational acceleration.

Bubble expansion from a flat interface to near detachment

is simulated for a full

range of Ca (0.01–100) and Bo

(0.01–0.5). The maximum gas pressure is found to vary

almost linearly with Ca for 0.01[les ]Ca[les ]100.

This correlation allows the maximum

bubble pressure method for measuring dynamic surface tension to

be extended to viscous liquids. Simulated detached bubble

volumes approach static values for Ca[Lt ]1,

and asymptote as Q3/4 for

Ca[Gt ]1, in agreement with analytic predictions.

In the limit Ca→0, two singular time domains are

identified near the beginning and the end of

bubble growth during which viscous and capillary forces

become comparable.

Expansion and contraction experiments were conducted using

a viscous silicone oil.

Digitized video images of deforming bubbles compare well with

numerical solutions.

It is observed that a bubble contracting at high

Ca snaps off.
The wave modes in ducted swirling flows
Authors: TAM CHRISTOPHER K. W. , AURIAULT LAURENT
Published: July 2002

The small-amplitude wave modes inside a ducted inviscid compressible
swirling flow
are investigated. In order to avoid possible mathematical ambiguities arising
from the
use of an inviscid flow model, the wave modes are cast as the solution
of an initial
boundary value problem. Two families of propagating waves are found. The
acoustic
modes are supported by the compressibility effect of the flow. The rotational
modes
are sustained by the centrifugal force field associated with the mean flow
rotation.
Two cases, one with a free-vortex swirl and the other with a rigid-body
swirl, are
investigated in some depth. Numerical results are provided.
Flow past a sphere up to a Reynolds number of 300
Authors: JOHNSON T. A. , PATEL V. C.
Published: July 2002

The flow of an incompressible viscous fluid past a sphere is investigated
numerically
and experimentally over flow regimes including steady and unsteady laminar
flow at
Reynolds numbers of up to 300. Flow-visualization experiments are used
to validate
the numerical results and to provide additional insight into the behaviour
of the flow.
Near-wake visualizations are presented for both steady and unsteady flows.

Calculations for Reynolds numbers of up to 200 show steady axisymmetric
flow and
compare well with previous experimental and numerical observations. For
Reynolds
numbers of 210 to 270, a steady non-axisymmetric regime is found, also
in agreement
with previous work. To advance the basic understanding of this transition,
a symmetry
breaking mechanism is proposed based on a detailed analysis of the calculated
flow
field.

Unsteady flow is calculated at Reynolds numbers greater than 270. The
results at a
Reynolds number of 300 show a highly organized periodic flow dominated
by vortex
shedding. An analysis of the calculated vortical structure of the wake
reveals a
sequence of shed hairpin vortices in combination with a sequence of previously

unidentified induced hairpin vortices. The numerical results compare favourably
with
experimental flow visualizations which, interestingly, fail to reveal the
induced vortices.
Based on the deduced symmetry-breaking mechanism, an analysis of the unsteady

kinematics, and the experimental results, a mechanism driving the transition
to
unsteady flow is proposed.
Boundary-layer instability noise on aerofoils
Authors: NASH EMMA C. , LOWSON MARTIN V. , McALPINE ALAN
Published: July 2002

An experimental and theoretical investigation has been carried
out to understand the
tonal noise generation mechanism on aerofoils at moderate Reynolds number.
Experiments
were conducted on a NACA0012 aerofoil section in a low-turbulence closed

working section wind tunnel. Narrow band acoustic tones were observed up
to 40 dB
above background noise. The ladder structure of these tones was eliminated
by modifying
the tunnel to approximate to anechoic conditions. High-resolution flow
velocity
measurements have been made with a three-component laser-Doppler anemometer

(LDA) which have revealed the presence of strongly amplified boundary-layer
instabilities
in a region of separated shear flow just upstream of the pressure surface

trailing edge, which match the frequency of the acoustic tones. Flow visualization

experiments have shown these instabilities to roll up to form a regular

Kármán-type vortex street.

A new mechanism for tonal noise generation has been proposed, based
on the
growth of Tollmien–Schlichting (T–S) instability
waves strongly amplified by inflectional
profiles in the separating laminar shear layer on the pressure surface
of the
aerofoil. The growth of fixed frequency, spatially growing boundary-layer
instability
waves propagating over the aerofoil pressure surface has been calculated
using
experimentally obtained boundary-layer characteristics. The effect of boundary-layer

separation has been incorporated into the model. Frequency selection and
prediction
of T–S waves are in remarkably good agreement with experimental data.
On the generation of vorticity at a free surface
Authors: LUNDGREN THOMAS , KOUMOUTSAKOS PETROS
Published: July 2002

The mechanism for the generation of vorticity at a viscous free
surface is described.
This is a free-surface analogue of Lighthill's strategy for determining
the vorticity flux
at solid boundaries. In this method the zero-shear-stress and pressure
boundary conditions
are transformed into a boundary integral formulation suitable for the velocity–vorticity

description of the flow. A vortex sheet along the free surface is determined
by
the pressure boundary condition, while the condition of zero shear stress
determines
the vorticity at the surface. In general, vorticity is generated at free
surfaces whenever
there is flow past regions of surface curvature. It is shown that vorticity
is conserved in
free-surface viscous flows. Vorticity which flows out of the fluid across
the free surface
is gained by the vortex sheet; the integral of vorticity over the entire
fluid region plus
the integral of ‘surface vorticity’ over the
free surface remains constant. The implications
of the present strategy as an algorithm for numerical calculations are
discussed.
The autonomous cycle of near-wall turbulence
Authors: JIMÉNEZ JAVIER , PINELLI ALFREDO
Published: July 2002

Numerical experiments on modified turbulent channels at moderate Reynolds numbers
are used to differentiate between several possible regeneration cycles for the
turbulent fluctuations in wall-bounded flows. It is shown that a cycle exists which is
local to the near-wall region and does not depend on the outer flow. It involves the
formation of velocity streaks from the advection of the mean profile by streamwise
vortices, and the generation of the vortices from the instability of the streaks. Interrupting
any of those processes leads to laminarization. The presence of the wall
seems to be only necessary to maintain the mean shear. The generation of secondary
vorticity at the wall is shown to be of little importance in turbulence generation
under natural circumstances. Inhibiting its production increases turbulence intensity
and drag.
Non-local two-dimensional turbulence and Batchelor's regime for passive scalars
Authors: NAZARENKO S. , LAVAL J.-P.
Published: July 2002

We study small-scale two-dimensional non-local turbulence, where interaction of
small scales with large vortices dominates in the small-scale dynamics, by using a
semi-classical approach developed in Dyachenko, Nazarenko & Zakharov (1992),
Nazarenko, Zabusky & Scheidegger (1995), Dubrulle & Nazarenko (1997) and
Nazarenko, Kevlahan & Dubrulle (1999). Also, we consider a closely related problem
of passive scalars in Batchelor's regime, when the Schmidt number is much greater
than unity. In our approach, we do not perform any statistical averaging, and most
of our results are valid for any form of the large-scale advection. A new invariant
is found in this paper for passive scalars when their initial spectrum is isotropic. It
is shown, analytically, numerically and using a dimensional argument, that there is a
spectrum corresponding to an inverse cascade of the new invariant, which scales like
k−1 for turbulent energy and k1 for passive
scalars. For passive scalars, the k1-spectrum was first found by
Kraichnan (1974) in the special case of advection δ-correlated in time, and until now it
was believed to correspond to an absolute thermodynamic equilibrium and not a cascade. We also
obtain, both analytically and numerically, power-law spectra of decaying two-dimensional
turbulence, k−2, and passive scalar, k0.
A numerical study of the motion of drops in Poiseuille flow.
Part 1. Lateral migration of one drop
Authors: MORTAZAVI SAEED , TRYGGVASON GRÉTAR
Published: July 2002

The cross-stream migration of a deformable drop in two-dimensional Hagen–Poiseuille
flow at finite Reynolds numbers is studied numerically. In the limit of a small Reynolds
number (< 1), the motion of the drop depends strongly on the ratio of the viscosity
of the drop fluid to the viscosity of the suspending fluid. For viscosity ratio 0.125 a
drop moves toward the centre of the channel, while for ratio 1.0 it moves away from
the centre until halted by wall repulsion. The rate of migration increases with the
deformability of the drop. At higher Reynolds numbers (5–50), the drop either moves
to an equilibrium lateral position about halfway between the centreline and the wall –
according to the so-called Segre–Silberberg effect or it undergoes oscillatory motion.
The steady-state position depends only weakly on the various physical parameters of
the flow, but the length of the transient oscillations increases as the Reynolds number
is raised, or the density of the drop is increased, or the viscosity of the drop is
decreased. Once the Reynolds number is high enough, the oscillations appear to persist
forever and no steady state is observed. The numerical results are in good agreement
with experimental observations, especially for drops that reach a steady-state lateral
position. Most of the simulations assume that the flow is two-dimensional. A few
simulations of three-dimensional flows for a modest Reynolds number (Re = 10), and
a small computational domain, confirm the behaviour seen in two dimensions. The
equilibrium position of the three-dimensional drop is close to that predicted in the
simulations of two-dimensional flow.
Beyond ‘Delegative Democracy’: ‘Old Politics’ and ‘New Economics’ in Latin America
Authors: PANIZZA FRANCISCO
Published: July 2002

For around 15 years Latin America has been undergoing an
unprecedented conjunction of political and economic change, from
authoritarianism to democracy and from a state-centred matrix of economic
development towards free-market economies. This article takes up the theme of
the links between politics and economic change in contemporary Latin America.
More specifically, it examines the relation between ‘old politics’ and ‘new
economics’. It has two main purposes: The first is to re-examine some of
modernisation theory's assumptions about the relations between political and
economic modernisation. The second, more specific to the Latin American
debate, is to question some of the dominant views about the nature of democracy
in the region, particularly Guillermo O'Donnell's influential ‘delegative
democracy’ model.
Plasmodium falciparum parasitaemia described by a new mathematical model
Authors: MOLINEAUX L. , DIEBNER H. H. , EICHNER M. , COLLINS W. E. , JEFFERY G. M. , DIETZ K.
Published: July 2002

A new mathematical model of Plasmodium falciparum asexual parasitaemia is formulated and fitted to 35 malaria therapy cases making a spontaneous recovery after primary inoculation. Observed and simulated case-histories are compared with respect to 9 descriptive statistics. The simulated courses of parasitaemia are more realistic than any previously published. The model uses a discrete time-step of 2 days. Its realistic behaviour was achieved by the following combination of features (i) intra-clonal antigenic variation, (ii) large variations of the variants' baseline growth rate, depending on both variant and case, (iii) innate autoregulation of the asexual parasite density, variable among cases, (iv) acquired variant-specific immunity and (v) acquired variant-transcending immunity, variable among cases. Aspects of the model's internal behaviour, concerning variant dynamics, as well as the respective contributions of the three control mechanisms (iii) – (v), are displayed. Some implications for pathogenesis and control are discussed.
Relative contribution of day-to-day and intra-specimen variation in faecal egg counts ofSchistosoma mansonibefore and after treatment with praziquantel
Authors: UTZINGER J. , BOOTH M. , N'GORAN E. K. , MÜLLER I. , TANNER M. , LENGELER C.
Published: July 2002

There is evidence that faecal egg counts ofSchistosoma mansonivary considerably from day to day, which results in poor sensitivity of single stool readings. Intra-specimen variation ofS. mansoniegg counts may also be considerable, but has previously been considered as the less important component. We quantified the relative contribution of these two sources of variation among 96 schoolchildren from an area in Côte d'Ivoire highly endemic forS. mansoni. Stool specimens were collected over 5 consecutive days, and 5 egg-counts were made in each specimen by the Kato–Katz technique. The point prevalence of the first sample was 42.7% and the cumulative prevalence after the maximum sampling effort was 88.5%. Using generalized linear mixed models we found that the presence ofS. mansonieggs in a stool sample varied much more between days than within specimens, indicating that stool sample examination over multiple days is required for accurate prevalence estimates. However, using the same approach, we found that among infected children intra-specimen variation in egg counts was 4.3 times higher than day-to-day variation. After praziquantel administration, day-to-day variation was more important than before, since most infections were very light and thus likely to be missed altogether by stool examination on a single day. We conclude that diagnostic sensitivity in high transmission areas is maximized by making several stool readings on several days, but examining 1 stool specimen several times can make reasonable estimates of infection intensity.
Onchocerca ochengi: epidemiological evidence of cross-protection
against
Onchocerca volvulus in man
Authors: WAHL G. , ENYONG P. , NGOSSO A. , SCHIBEL J. M. , MOYOU R. , TUBBESING H. , EKALE D. , RENZ A.
Published: July 2002

In North Cameroon, the vector of Onchocerca volvulus (causative

agent of human onchocerciasis) also transmits 2 filariae
of animals: O. ochengi from cattle and O. ramachandrini
from
wart hogs. In order to assess the qualitative and quantitative
roles of these ‘animal filariae’ in the epidemiology of
O. volvulus, the transmission of the 3 parasites was measured
in 2
villages and related to the endemicity of human onchocerciasis. In Galim,
a
cattle-farming Guinea savanna village where
wild animals are rare, the overwhelming majority of all filarial infections

found in the Simulium damnosum s.l. vectors
throughout the year were O. ochengi (89%). The remaining infections

were mainly O. volvulus (10·5%), and a few O.
ramachandrini (0·5%). In Karna, a crop-farming Sudan savanna

village where cattle are rare, but wild animals common,
flies were also more frequently infected with animal filariae than with

the human parasite. In the dry season, when nomadic
cattle are present, 54% of all infections were O. ochengi,
36% O. volvulus and 10% O. ramachindrini. In the rainy
season,
when the cattle move away, flies were mainly infected with O.
ramachandrini (52% of all infections) and secondly with
O. volvulus (48%). In Karna, the relationship between the Annual

Transmission Potential (ATP) of O. volvulus and its
prevalence in the human population conformed to other onchocerciasis foci,

in that a moderate ATP led to hyperendemic
onchocerciasis. In Galim, however, a 7-fold higher O. volvulus-ATP

(caused by a very high biting rate of the flies)
contrasted with a strikingly low endemicity of onchocerciasis. Since, at
the
same time, in Galim the transmission of O. ochengi (measured on

man) was very high (15000 L3/fly collector/year), we hypothesize

that the reduced endemicity of onchocerciasis in Galim is due to
‘natural heterologous vaccination’ by the large annual number
of
O. ochengi-L3, inoculated into man by anthropo-boophilic
S. damnosum s.l. The importance of micro-epidemiology for the
understanding
of the interlinkage of human and animal onchocerciasis is discussed.
Tissue cyst tropism in Toxoplasma gondii: a comparison of

tissue cyst formation in organs of cats, and rodents fed oocysts
Authors: DUBEY J. P.
Published: July 2002

The persistence of Toxoplasma gondii tissue cysts in organs

of cats (definitive host) and rodents (intermediate hosts) was

studied. Nine cats, 12 rats, and 12 mice were fed T. gondii

oocysts and their organs were digested in pepsin and then

bioassayed for bradyzoites in mice. Of 9 cats killed 37 or 51 days after

feeding 102 (2 cats), 103 (3 cats) or 104

(4 cats) oocysts

of the VEG strain, tissue cysts were found in each cat; in the tongue of

9, in the heart of 5, in the brain of 4, and in the

eyes of 1 cat. The dose had no effect on the distribution of tissue cysts

in cats. Twelve rats were each fed 105 oocysts of

the VEG strain of T. gondii and killed 21, 29, 64 or 237 days
later.

At each time-period, 11 tissues of 3 rats were pooled

and bioassayed in mice. Tissue cysts were found in the brain, skeletal

muscle, heart and kidneys of rats at each killing time;

in the lungs, intestines, and mesenteric lymph nodes in 3 of 4 instances;

in the tongue, liver, and eyes in 2 instances and

in the spleen in 1 instance. Also, using the same procedures and sampling

the same 11 tissues as used for rats, tissue cysts

were seen in all organs except in the tongue and liver of 3 mice killed

on day 82 after feeding the VEG strain. In 9 mice

(3 with each strain) fed oocysts of the ME-49, GT-1, or P89 T. gondii

strain and killed 62–130 days later, tissue cysts were

found consistently only in the brain. Thus, in rats and mice, most

tissue cysts were found in the brain and rarely in the

tongue. This was in marked contrast to the distribution of tissue cysts
in cats.
Mathematical modelling of the within-host dynamics of Plasmodium falciparum
Authors: HOSHEN M. B. , HEINRICH R. , STEIN W. D. , GINSBURG H.
Published: July 2002

The development of malaria due to Plasmodium falciparum is a complex, multi-stage process. It is usually characterized
by an exponential growth in the number of parasite-infected erythrocytes, followed by marked oscillations in this number
with a period of 48 h, which are eventually dampened. This course of events has been the subject of various mathematical
models. In this paper we propose a new mathematical model for the in-host asexual erythrocytic development of P.
falciparum malaria. Synchronicity of the infection is shown to be an inherent feature of infection, irrespective of the
duration of merozoite release from the liver. It will, therefore, cause periodic symptoms, as known in malaria patients. We
also simulate the effects of an induced host immune response and show how the level of immunity affects the development
of disease. The simulations fit well with the clinical observations. We show how infection can become asynchronous and
discuss the effect of desynchronization on the circulating and total parasitaemia and demonstrate that synchronized broods
will show parasitaemia fluctuations.
Psychopathology, childhood sexual abuse and other childhood adversities: relative links to subsequent suicidal behaviour in the US
Authors: MOLNAR B. E. , BERKMAN L. F. , BUKA S. L.
Published: July 2002

Background. Research shows that psychopathology, child sexual abuse and other childhood adversities are risk factors for suicide. However, few have investigated their joint and independent roles in the pursuit of a reliable, predictive model of suicidal behaviour.

Methods. Data are from the National Comorbidity Survey (N = 5877), a nationally representative study of prevalence, risk factors, and social consequences of psychiatric disorders in the US. Discrete time survival analysis and population attributable risk methodologies were utilized.

Results. Among those sexually abused as children, odds of suicide attempts were 2–4 times higher among women and 4–11 times higher among men, compared with those not abused, controlling for other adversities. Odds ratios were reduced but most remained statistically significant after adjusting for lifetime psychiatric illnesses preceding suicide attempts. In the same predictive equation, 79% of serious suicide attempts among women could be attributed to psychiatric disorders while 12% was attributable to rape and 7% to molestation. The highest probability of a first attempt was during early adolescence for those who were sexually abused and had a lifetime disorder, but it was 8–12 years older for those sexually abused without any disorders.

Conclusions. In the US, a strong association exists between child sexual abuse and suicidal behaviour, mediated by psychopathology. There is a substantial proportion of suicide risk attributable to child sexual abuse beyond the presence of psychopathology and other adversities. From a clinical standpoint, abuse survivors represent a high-risk population for suicidal behaviour. Further research into this preventable antecedent of suicide attempts is necessary.
Prevalence of mental disorders and psychosocial

impairments in adolescents and young adults
Authors: WITTCHEN H.-U. , NELSON C. B. , LACHNER G.
Published: July 2002

Background. As part of a longitudinal study, prevalence

findings of DSM-IV disorders are presented

for a random sample of 3021 respondents aged 14 to 24, with

response rate 71%.

Method. Assessment included various subtypes of disorders,

subthreshold conditions and disorders

that have only rarely been studied in other epidemiological surveys.

The computer-assisted Munich-Composite International Diagnostic

Interview (M-CIDI) was used to derive DSM-IV diagnoses.

Results. Substance disorders were the most frequent

(lifetime 17·7%; 12-month 11·4%), with abuse

being considerably more frequent than dependence. Other

mental disorders had a lifetime

prevalence of 27·5% (12-month, 17·5%) with

depressive disorders (16·8%) being more frequent

than anxiety disorders (14·4%). Eating disorders (3·0%)

and threshold somatoform disorders

(1·2%) were rare disorders. Subthreshold anxiety and

somatoform disorders, however, were more

frequent than threshold disorders. Prevalence of disorders was

equally high for males and females,

although specific disorder prevalence varied significantly by

gender. The co-occurrence of disorders

(co-morbidity) was substantial and was significantly related to

greater reductions in work

productivity and increased rates of professional helpseeking behaviour.

Conclusions. Findings underline that mental disorders in

young adults are frequent and impairing,

limiting work and education ability and social interaction. Given

the fact that adolescents and

young adults are in a key phase of socialization in terms of

professional career and interpersonal

relationships, our findings indicate a considerable risk potential

for an accumulation of complicating

factors and future chronicity. This paper is the first report

of this ongoing longitudinal study about

early developmental conditions of mental disorders.
Capacity limitations in short-term memory in
schizophrenia: tests of competing hypotheses
Authors: GOLDBERG T. E. , PATTERSON K. J. , TAQQU Y. , WILDER K.
Published: July 2002

Background. Capacity limitation theories have proved to

be surprisingly resilient in characterizing
some of the cognitive deficits in schizophrenia. However, this perspective

has not generally been
applied to short-term verbal memory tasks. We explored this issue by
first attempting to ascertain
if gross misallocations of processing resources might explain
impairments in short-term memory in
schizophrenia on a classic digit span task and in a second study
by attempting to determine what
effects delay and memory set size had on a divided attention short-term
verbal memory paradigm.

Methods. In the first study 16 patients with schizophrenia

and 21 normal controls received 40 trials of
a three digit task and 20 trials of a six digit span task. As the absolute

number of digits presented
and duration of presentation in two conditions were identical, subjects
thus had equivalent
‘opportunities’ to make errors if distraction, in the
sense of misallocation of cognitive resources,
were at the root of poor performance. In the second study 15 patients with
schizophrenia and 15
normal controls were tested in conditions in which two, four or six words
were presented and in
which rehearsal was prevented by an interference task (colour naming)
for delays of 5, 10 or 15 s.

Results. Patients had disproportionate difficulty on the
six digit rather than the three digit condition,
suggesting that deficits in the verbal working memory short-term store
may not be the result of
attentional factors. In the second study, patients' performance
was differentially worsened by the
interference task, by memory set size (i.e. a capacity limitation) and

by delay, a measure of decay rate.

Conclusions. In concert, these studies demonstrate that
schizophrenia patients have difficulties on
verbal short-term memory span tasks not because of misallocation of
resources, but rather because
of limitations in ‘representational capacity’ and
maintenance of information over delays.
Are computerized interviews equivalent to human
interviewers? CIDI-Auto versus CIDI in anxiety and
depressive disorders
Authors: PETERS L. , CLARK D. , CARROLL F.
Published: July 2002

Background. The equivalency of the Composite International

Diagnostic Interview delivered by
human interviewers (CIDI) and its computerized version (CIDI-Auto) was
examined for anxiety
and depressive disorders.

Methods. Subjects were 40 patients at an Anxiety Disorders
Clinic
and 40 general medical practice
attenders. The CIDI-Auto and CIDI were administered in counterbalanced
order on the same day
and measures of computer attitudes and the acceptability of the two interview
formats were also
taken.

Results. The CIDI-Auto and the CIDI were found to be
equally acceptable to subjects on the
dimensions of comfort and preference, while the CIDI-Auto was
rated as less embarrassing but too
long in comparison with the CIDI. The agreement between the two formats
was acceptable with
kappa values for ICD-10 diagnoses being above 0·65 and for
DSM-III-R diagnoses above 0·5 except
for two diagnoses (generalized anxiety disorder and dysthymia). Discrepancies
between the two
formats were predicted by computer attitudes and not by computer experiences
or the tendency to
respond in a socially desirable fashion.

Conclusions. It is concluded that the CIDI-Auto in its
self-administered form is an acceptable
substitute for the CIDI for suitable subjects.
Prevalence of depression in an elderly community
sample: a comparison of GMS-AGECAT and
DSM-IV diagnostic criteria
Authors: NEWMAN S. C. , SHELDON C. T. , BLAND R. C.
Published: July 2002

Background. Prevalence rates of depression based on the
GMS-AGECAT system are markedly
higher than rates of major depression diagnosed using DSM-III and DSM-III-R
criteria.
Interpreting this finding is difficult since AGECAT diagnostic criteria
have not been published.

Methods. We conducted a survey in Edmonton, Canada, in which
1119 community residents aged
65 years or older were administered the Geriatric Mental State (GMS) questionnaire.
Depression
was diagnosed using AGECAT and also according to criteria for DSM-IV major
depression and
minor depression. We identified 57 items in the GMS relating to major and
minor depression which
were then grouped into dysphoric, somatic and cognitive categories. The
relationship of these
symptoms to AGECAT depression was investigated by recoding symptoms to
absent (nullifying)
and recalculating the number of AGECAT cases. Data were weighted to reflect
the underlying
population.

Results. There were 143 cases of AGECAT depression (prevalence
rate=11·4%), 14 cases of major
depression (prevalence rate=0·86%) and 44 cases of minor depression
(prevalence rate=3·6%).
Of the 154 subjects with either AGECAT or DSM-IV depression, only 47 (31%)
were depressed
according to both diagnostic systems. Nullifying all dysphoric symptoms
reduced the number of
AGECAT cases to eight, whereas nullifying somatic and cognitive symptoms
reduced the numbers
of cases only to 138 and 142, respectively. By themselves, dysphoric symptoms
accounted for 77 of
the 143 cases of AGECAT depression, while somatic and cognitive symptoms
alone accounted for
no cases.

Conclusions. AGECAT depression is more inclusive than DSM-IV
major or minor depression and
AGECAT case status is determined mainly by the proportion of dysphoric
symptoms.
The first contact of patients with schizophrenia with
psychiatric services: social factors and pathways to
care in a multi-ethnic population
Authors: BURNETT R. , MALLETT R. , BHUGRA D. , HUTCHINSON G. , DER G. , LEFF J.
Published: July 2002

Background. African-Caribbean patients have less desirable
routes of entry into the psychiatric
services than other ethnic groups in Britain but this may not apply to
the first
contact with services.

Methods. Patients' pathways to care, type of admission
or referral and sectioning details were
recorded for all first contact patients presenting to south London psychiatric
services over a 2-year
period. We also conducted a retrospective analysis of data from the Camberwell
Register,
comparing rates of compulsory admission between ‘Whites’
and ‘African-Caribbeans’ for first
and readmissions, over a 20-year period.

Results. Our first contact sample comprised 38 White, 38 African-Caribbean
and 24 Asian patients
with CATEGO defined broad schizophrenia. GP referral was found to be the
most common mode
of contact and there were no significant differences between the ethnic
groups with regard to
compulsory admission. Similarly, data from the Camberwell Register showed
no significant
difference in rates of compulsory admission between first admission White
and African-Caribbean
patients. However, when all readmissions were examined, African-Caribbeans
were more likely to
be admitted involuntarily.

Conclusions. Our findings suggest that reports of less desirable
routes of entry for
African-Caribbean patients into the psychiatric service do not apply to
their first admission but are likely
to develop over time and repeated contact with the services.
Safety of fluoxetine during the first trimester of
pregnancy: a meta-analytical review of epidemiological studies
Authors: ADDIS ANTONIO , KOREN GIDEON
Published: July 2002

Background. This study was designed to examine whether there is an increased risk for major
malformations following the use of fluoxetine during the first trimester of pregnancy.

Methods. Published and unpublished reports were identified through computerized and manual
searches of bibliographical databases, reference lists from primary articles, and letters to editors,
agencies, foundations and content experts. Meta-analysis was undertaken of prospective controlled
and uncontrolled studies on the use of fluoxetine during first trimester of pregnancy.

Results. The pooled relative risk and 95% confidence interval for major malformations does not
suggest an association between the use of fluoxetine during the first trimester and an increased risk
of major malformations. Combination of controlled and uncontrolled studies shows a weighted risk
of 2·6% (95% CI 1–4·2%). The summary odds ratio from the two controlled studies (OR = 1·33,
95% CI 0·49–3·58) was not significant. Homogeneity testing shows that the effect sizes are similar
throughout all studies. Power analysis indicates that 26 controlled studies of similar size, would be
required, to reverse this finding.

Conclusions. The use of fluoxetine during the first trimester of pregnancy is not associated with
measurable teratogenic effects in human.