bluuebunny/crossref_metadata_2025 huggingface dataset:
INFANT AND CHILD MORTALITY DETERMINANTS IN BANGLADESH: ARE THEY CHANGING?
Authors: MAJUMDER ABUL KASHEM , MAY MARIAN , DEV PANT PRAKASH
Published: July 2002

From the data of the 1989 Bangladesh Fertility Survey, aggregate deaths reported at ages 0-12 and 13-60 months are used to estimate infant and child mortality. Multivariate analysis shows that preceding birth interval length, followed by survival status of the immediately preceding child, are the most important factors associated with differential infant and child mortality risks; sex of the index child and mother's and father's education are also significant. Demographic factors are influential during infancy as well as childhood, but social factors, particularly mother's and father's education, now emerge as significant predictors of infant mortality risks. This indicates a change in the role of socioeconomic factors, since the earlier Bangladesh Fertility Survey in 1975.
DETERMINANTS OF CONTRACEPTIVE USE AMONG WOMEN OF REPRODUCTIVE AGE IN GREAT BRITAIN AND GERMANY I: DEMOGRAPHIC FACTORS
Authors: ODDENS B. J. , LEHERT P.
Published: July 2002

Multifactorial analyses of data from representative British and German national contraception surveys were used to examine the principal demographic determinants of contraceptive use by women. Contraceptive use appeared to be determined mainly by reference to ‘reproductive status’ (the combined impact of age, marital status, parity and future child wish). Women who were postponing pregnancies were using oral contraceptives, whereas those who wanted no more children relied more on intrauterine devices or sterilisation. Differences between the countries suggested that the choice of contraceptive method was influenced by health care policy, the organisation of the relevant services and differential provider preferences. The contraceptive method used was also related to having occasional rather than steady sexual partners (more condom use), lower educational level (less oral contraceptive use) and frequent church attendance (greater use of condoms and periodic abstinence). Contraception decisions appeared to follow a fixed pattern, based more on a couple's demographic situation (reproductive status, country, educational level and religious beliefs) than on the characteristics of the contraceptive methods. This resulted in an unnecessarily restricted choice of methods.
BELIEFS ABOUT CHILDREN'S ILLNESS
Authors: PEBLEY ANNE , HURTADO ELENA , GOLDMAN NOREEN
Published: July 2002

Beliefs about child illness were investigated using semi-structured interviews with mothers and providers in four rural Guatemalan communities. The two most common forms of child illness in Guatemala – diarrhoea and respiratory disease – were focused upon. These illnesses are particularly difficult to prevent and treat, especially with the rudimentary health services available in rural areas of developing countries. Comparisons with other ethnographic studies in Guatemala suggest that some traditional models of illness causation identified in these earlier investigations are relatively unimportant in the communities studied here. This finding, in conjunction with frequent responses related to hygiene and water, suggests that traditional explanations may be co-existing with biomedical views of illness causation to a greater degree today than in the past.
SECULAR TREND IN AGE AT MENARCHE IN CHINA: A CASE STUDY OF TWO RURAL COUNTIES IN ANHUI PROVINCE
Authors: GRAHAM MAUREEN J. , LARSEN ULLA , XU XIPING
Published: July 2002

There is increasing evidence that age at menarche has decreased in Europe and the United States during the last century and in Japan over the last several decades. Data from a community-based survey conducted in two rural counties of Anhui Province in China indicate a similar, downward secular trend in age at menarche for Chinese women. The present study shows the mean age at menarche decreased by 2·8 years, from 16·5 to 13·7, over an approximate 40-year time interval. This rapid decrease in age at menarche may partly be due to better nutrition and living standards reflected by the improved socioeconomic standards experienced in China over the past few decades. To test this hypothesis, a number of determinants of age at menarche were assessed; year of birth, literacy status, county of residence, amount of physical labour, general health status, pesticide exposure before age at menarche, and drinking water source were all found to be associated with age at menarche.
COMMUNITY PERCEPTIONS OF REASONS FOR PREFERENCE FOR CONSANGUINEOUS MARRIAGES IN PAKISTAN
Authors: HUSSAIN R.
Published: July 2002

Although the recent Pakistan Demographic and Health Survey (DHS) show that two-thirds of marriages in Pakistan are consanguineous, the sociocultural determinants of such marriages remain largely unexplored. This paper examines the relative importance of the three commonly perceived reasons for such marriages: religious, economic and cultural. The analysis is based on qualitative data collected in 1995 from multi-ethnic and multi-religious communities in Karachi, the largest city of Pakistan. Results show that consanguineous marriages are preferred across all ethnic and religious groups to a varying degree, and that parents continue to be the prime decision-makers for marriages of both sons and daughters. The major reasons for a preference for consanguineous marriages are sociocultural rather than any perceived economic benefits, either in the form of consolidation of family property or smaller and less expensive dowries. Among Muslims, following religious traditions is the least commonly cited reason for such marriages. Despite the reported sociocultural advantages of consanguineous marriages, such unions are perceived to be exploitative as they perpetuate the existing power structures within the family.
Varying influence of the autolysin, N-acetyl muramidase, and the cell
envelope proteinase on the rate of autolysis of six commercial
Lactococcus lactis cheese starter bacteria grown in milk
Authors: GOVINDASAMY-LUCEY SELVARANI , GOPAL PRAMOD K. , SULLIVAN PATRICK A. , PILLIDGE CHRISTOPHER J.
Published: July 2002

The autolysin, N-acetyl muramidase (AcmA), of six commercial
Lactococcus lactis subsp. cremoris starter strains and eight Lc. lactis subsp. cremoris
derivatives or plasmid-free strains was shown by renaturing SDS-PAGE (zymogram
analysis) to be degraded by the cell envelope proteinase (lactocepin; EC 3.4.21.96)
after growth of strains in milk at 30 °C for 72 h. Degradation of AcmA was
less in starter strains and derivatives producing lactocepin I/III (intermediate
specificity) than in strains producing lactocepin I. This supports previous
observations on AcmA degradation in derivatives of the laboratory strain Lc. lactis
subsp. cremoris MG1363 (Buist et al. Journal of Bacteriology180 5947–5953 1998). In
contrast to the MG1363 derivatives, however, the extent of autolysis in milk of the
commercial Lc. lactis subsp. cremoris starter strains in this study did not always
correlate with lactocepin specificity and AcmA degradation. The distribution of
autolysins within the cell envelope of Lc. lactis subsp. cremoris starter strains and
derivatives harvested during growth in milk was compared by zymogram analysis.
AcmA was found associated with cell membranes as well as cell walls and some
cleavage of AcmA occurred independently of lactocepin activity. An AcmA product
intermediate in size between precursor (46 kDa) and mature (41 kDa) forms of AcmA
was clearly visible on zymograms, even in the absence of lactocepin I activity. These
results show that autolysis of commercial Lc. lactis subsp. cremoris starter strains is
not primarily determined by AcmA activity in relation to lactocepin specificity and
that proteolytic cleavage of AcmA in vivo is not fully defined.
Polysaccharide production by kefir grains during whey fermentation
Authors: RIMADA PABLO SEBASTIÁN , ABRAHAM ANALÍA GRACIELA
Published: July 2002

Fermentation of deproteinised whey with kefir grains CIDCA AGK1 was studied focusing on polysaccharide production from lactose. Kefir grains were able to acidify whey at different rates depending on the grain/whey ratio. During fermentation, kefir grains increased their weight and a water-soluble polysaccharide was released to the media. Exopolysaccharide concentration increased with fermentation time, reaching values of 57·2 and 103·4 mg/l after 5 days of fermentation in cultures with 10 and 100 g kefir grains/l, respectively. The polysaccharide fraction quantified after fermentation corresponded to the soluble fraction, because part of the polysaccharide became a component of the grain. Weight of kefir grains varied depending on the time of fermentation. Polysaccharide production was affected by temperature. Although the highest concentration of polysaccharide in the media was observed at 43 °C at both grain/whey ratios, the weight of the grains decreased in these conditions. In conclusion, kefir grains were able to acidify deproteinised whey, reducing lactose concentration, increasing their weight and producing a soluble polysaccharide.
Hypocholesterolemic effect of Lactobacillus gasseri SBT0270 in rats fed a cholesterol-enriched diet
Authors: USMAN  , HOSONO AKIYOSHI
Published: July 2002

The effects of administration of Lactobacillus gasseri SBT0270 on serum lipids and bile acids, faecal bile acids and microflora were estimated in hypercholesterolemic rats. An effective dose of strain SBT0270 to exert its hypocholesterolemic effect was 109 viable cells/d. The dose of 109 cells/d did not affect the faecal coliform counts, but the number of faecal lactobacilli in rats fed this dose was significantly higher than that in the control group observed at the end of feeding period. Hypocholesterolemic effect of Lb. gasseri SBT0270 was attributed to its ability to suppress the reabsorption of bile acids into the enterohepatic circulation and to enhance the excretion of acidic steroids in faeces of hypercholesterolemic rats.
Preparation and characterization of the N and C monoferric lobes
of buffalo lactoferrin produced by proteolysis using proteinase K
Authors: SHARMA SUJATA , SINGH TEJ P. , BHATIA KRISHAN L.
Published: July 2002

The two glycosylated N- and C-terminal lobes of buffalo lactoferrin
have
been produced by limited proteolysis using proteinase K. Lactoferrin is
a single chain
glycoprotein of molecular mass 80 kDa with two iron-binding sites and two
structural lobes connected by a short peptide. Purified samples of lactoferrin,
isolated from buffalo colostrum, were subjected to hydrolysis using trypsin,
chymotrypsin, pepsin, subtilisin and proteinase K. The first three proteinases
produced two major fragments of approximately 35 and 23 kDa together with
small
molecular mass peptides. Trypsin and chymotrypsin partly digested lactoferrin,
while pepsin converted all the intact lactoferrin into fragments. Subtilisin
hydrolysis
produced fragments of 40 and 26 kDa together with low molecular mass peptides.
However, SDS-PAGE of the proteinase K hydrolysis product gave a clear band
at
40 kDa together with a band indicating a substantial quantity of low molecular
mass
peptides (<14·4 kDa). Upon ion-exchange chromatography this product
gave two
major fractions, which were further purified by gel filtration and identified
as the C
and N lobes from their N-terminal sequences. Thus, the 40 kDa band in SDS-PAGE
of the proteinase K hydrolysis product contained two fragments of equal
molecular
mass. On further hydrolysis with proteinase K, the N lobe was completely
hydrolysed into low molecular mass peptides, while only a small fraction
of the C
lobe was converted into small products. This suggested that an inhibitory
fragment
was present in the C lobe that was released on hydrolysis to small fragments
and
prevented complete digestion of the C lobe by high-affinity binding to
the active site
of proteinase K. This fragment was isolated from the lactoferrin–proteinase
K
complex and its sequence determined to be
Val–Ala–Gln–Gly–Gly–Ala–Ala–Gly–Leu–Ala.
Circular dichroism studies indicated a high α-helical content in
the native
lactoferrin while comparatively lower helical structures were present in
the N and C
lobes. In addition, the iron saturations of the N and C lobes appeared
to be lower
than that of the native protein.
An experimental study of a boundary layer that is maintained on the verge of separation
Authors: ELSBERRY K. , LOEFFLER J. , ZHOU M. D. , WYGNANSKI I.
Published: July 2002

A boundary layer maintained as close as possible to separation over an extended
distance was produced, in accordance with the concept of Stratford. The resulting
layer was two-dimensional in the mean, had nearly a constant shape factor of
2.5 and approximately linear streamwise growth of its integral length scales. The
flow exhibited a definite non-equilibrium character, indicated by the different scales
required for collapse of the mean velocity and turbulence intensity profiles. It was also
very sensitive to the thickness of the upstream boundary layer. External excitation was
imposed for diagnostic purposes and as a tool for delaying separation. The oscillatory
momentum level of cμ ≈ 0.1% was tested for its ability to increase the skin friction
cf at the prescribed geometry. Various frequencies, corresponding to the Strouhal
number 0.008 < fθ0/Uref < 0.064,
were used for the free stream reference velocity of Uref = 15 m s−1 and
for two different inflow conditions. Notable increase (close
to 60%) in cf was observed at higher frequencies that did not undergo maximum
amplification. The increase in cf was accompanied by a reduction in the boundary
layer thickness and in the shape factor H. The latter decreased in one case from 2.5 to
2.1. The overall turbulence level in the boundary layer decreased due to the addition
of plane external perturbations.
Swirling flow of viscoelastic fluids. Part 2. Elastic effects
Authors: STOKES JASON R. , GRAHAM LACHLAN J. W. , LAWSON NICK J. , BOGER DAVID V.
Published: July 2002

A torsionally driven cavity has been used to examine the influence of elasticity
on the swirling flow of constant-viscosity elastic liquids (Boger fluids). A wealth
of phenomena is observed as the degree of inertia, elasticity and viscous forces
are varied by using a range of low- to high-viscosity flexible polyacrylamide Boger
fluids and a semi-rigid xanthan gum Boger fluid. As the inertia is decreased and
elasticity increased by using polyacrylamide Boger fluids, the circulation rates for
a ‘Newtonian-like’ secondary flow decreases until flow reversal occurs owing to the
increasing magnitude of the primary normal stress difference. For each polyacrylamide
fluid, the flow becomes highly unstable at a critical combination of Reynolds number
and Weissenberg number resulting in a new time-dependent elastic instability. Each
fluid is characterized by a dimensionless elasticity number and a correlation with
Reynolds number is found for the occurrence of the instability. In the elasticity
dominated flow of the polyacrylamide Boger fluids, the instability disrupts the flow
dramatically and causes an increase in the peak axial velocity along the central axis
by as much as 400%. In this case, the core vortex spirals with the primary motion
of fluid and is observed in some cases at Reynolds numbers much less than unity.
Elastic ‘reverse’ flow is observed for the xanthan gum Boger fluid at high Weissenberg
number. As the Weissenberg number decreases, and Reynolds number increases,
counter-rotating vortices flowing in the inertial direction form on the rotating lid.
The peak axial velocity decreases for the xanthan gum Boger fluid with decreasing
Weissenberg number. In addition, several constitutive models are used to describe
accurately the rheological properties of the fluids used in this work in shear and
extensional flow. This experimental investigation of a complex three-dimensional flow
using well-characterized fluids provides the information necessary for the validation
of non-Newtonian constitutive models through numerical analysis of the torsionally
driven cavity flow.
Linear stability of a gas boundary layer flowing past a thin liquid film over a flat plate
Authors: PELEKASIS NIKOLAOS A. , TSAMOPOULOS JOHN A.
Published: July 2002

The flow of a gas stream past a flat plate under the influence of rainfall is investigated.
As raindrops sediment on the flat plate, they coalesce to form a water film that flows
under the action of shear from the surrounding gas stream. In the limit of (a) large
Reynolds number, Re, in the gas phase, (b) small rainfall rate, r˙, compared to the
free-stream velocity, U∞, and (c) small film thickness compared to the thickness of the
boundary layer that surrounds it, a similarity solution is obtained that predicts growth
of the liquid film like x3/4; x denotes dimensionless distance from the leading edge.
The flow in the gas stream closely resembles the Blasius solution, whereas viscous
dissipation dominates inside the film. Local linear stability analysis is performed,
assuming nearly parallel base flow in the two streams, and operating in the triple-deck regime. Two distinct families of eigenvalues are identified, one corresponding
to the well-known Tollmien–Schlichting (TS) waves that originate in the gas stream,
and the other corresponding to an interfacial instability. It is shown that, for the
air–water system, the TS waves are convectively unstable whereas the interfacial
waves exhibit a pocket of absolute instability, at the streamwise location of the
applied disturbance. Moreover, it is found that as the inverse Weber number (We−1)
increases, indicating the increasing effect of surface tension compared to inertia, the
pocket of absolute instability is translated towards larger distances from the leading
edge and the growth rate of unstable waves decreases, until a critical value is reached,
We−1 ≈ We−1c,
beyond which the family of interfacial waves becomes convectively
unstable. Increasing the inverse Froude number (Fr−1), indicating the increasing
effect of gravity compared to inertia, results in the pocket of absolute instability shrinking until a critical value is
reached, Fr−1 ≈ Fr−1c, beyond which the family
of interfacial waves becomes convectively unstable. As We−1 and Fr−1
are further increased, interfacial waves are eventually stabilized, as expected. In this context,
increasing the rainfall rate or the free-stream velocity results in extending the region
of absolute instability over most of the airfoil surface. Owing to this behaviour it
is conjectured that a global mode that interacts with the boundary layer may arise
at the interface and, eventually, lead to three-dimensional waves (rivulets), or, under
extreme conditions, even premature separation.
A computational model of the collective fluid
dynamics of motile micro-organisms
Authors: HOPKINS MATTHEW M. , FAUCI LISA J.
Published: July 2002

A mathematical model and numerical method for studying the collective dynamics of
geotactic, gyrotactic and chemotactic micro-organisms immersed in a viscous fluid is
presented. The Navier–Stokes equations of fluid dynamics are solved in the presence
of a discrete collection of micro-organisms. These microbes act as point sources
of gravitational force in the fluid equations, and thus affect the fluid flow. Physical
factors, e.g. vorticity and gravity, as well as sensory factors affect swimming speed and
direction. In the case of chemotactic microbes, the swimming orientation is a function
of a molecular field. In the model considered here, the molecules are a nutrient whose
consumption results in an upward gradient of concentration that drives its downward
diffusion. The resultant upward chemotactically induced accumulation of cells results
in (Rayleigh–Taylor) instability and eventually in steady or chaotic convection that
transports molecules and affects the translocation of organisms. Computational results
that examine the long-time behaviour of the full nonlinear system are presented.

The actual dynamical system consisting of fluid and suspended swimming
organisms is obviously three-dimensional, as are the basic modelling equations. While
the computations presented in this paper are two-dimensional, they provide results
that match remarkably well the spatial patterns and long-time temporal dynamics
of actual experiments; various physically applicable assumptions yield steady states,
chaotic states, and bottom-standing plumes. The simplified representation of microbes
as point particles allows the variation of input parameters and modelling details, while
performing calculations with very large numbers of particles (≈104–105), enough so
that realistic cell concentrations and macroscopic fluid effects can be modelled with
one particle representing one microbe, rather than some collection of microbes. It
is demonstrated that this modelling framework can be used to test hypotheses concerning
the coupled effects of microbial behaviour, fluid dynamics and molecular
mixing. Thus, not only are insights provided into the differing dynamics concerning
purely geotactic and gyrotactic microbes, the dynamics of competing strategies for
chemotaxis, but it is demonstrated that relatively economical explorations in two
dimensions can deliver striking insights and distinguish among hypotheses.
Experiments on laminar film flow along a periodic wall
Authors: VLACHOGIANNIS M. , BONTOZOGLOU V.
Published: July 2002

Experimental results are reported on the structure of gravity-driven film flow along an
inclined periodic wall with rectangular corrugations. A fluorescence imaging method
is used to capture the evolution of film height in space and time with accuracy of a
few microns. The steady flow is found to exhibit a statically deformed free surface, as
predicted by previous asymptotic and numerical studies. Though usually unstable, its
characteristics determine much of the subsequent non-stationary dynamics. Travelling
disturbances are observed to evolve into solitary multi-peaked humps, and pronounced
differences from the respective phenomena along a flat wall are noted. Finally, a
remarkable stabilization of the flow at high Reynolds numbers is documented, which
proceeds through the development of a three-dimensional flow structure and leads to
a temporary decrease in film thickness and recession of solitary waves.
Flow past a cylinder close to a free surface
Authors: SHERIDAN J. , LIN J.-C. , ROCKWELL D.
Published: July 2002

Flow past a cylinder beneath a free surface gives rise to

fundamental classes of nearwake structure that are distinctly different

from the wake of a completely submerged cylinder. A central feature is

the generation of a vorticity layer from the free surface due to:

localized separation, in the form of small-scale breaking of a

free-surface wave; or complete separation from the free surface. This

vorticity layer appears adjacent to a layer from the surface of the

cylinder, thereby forming a jet-like flow. It is shown that the

instantaneous vorticity flux on either side of this jet is rapidly

balanced immediately after the onset of separation from the free

surface.
Erosion by planar turbulent wall jets
Authors: HOGG ANDREW J. , HUPPERT HERBERT E. , DADE W. BRIAN
Published: July 2002

New scaling laws are presented for the spatial variation of the mean
velocity and
lateral extent of a two-dimensional turbulent wall jet, flowing over a fixed rough
boundary. These scalings are analogous to those derived by Wygnanski
et al. (1992)
for the flow of a wall jet over a smooth boundary. They reveal that the
characteristics
of the jet depend weakly upon the roughness length associated with the boundary, as
confirmed by experimental studies (Rajaratnam 1967).

These laws are used in the development of an analytical framework to model the
progressive erosion of an initially flat bed of grains by a turbulent jet. The
grains are
eroded if the shear stress, exerted on the grains at the surface of the bed,
exceeds a
critical value which is a function of the physical characteristics of the
grains. After
the wall jet has been flowing for a sufficiently long period, the boundary attains a
steady state, in which the mobilizing forces associated with the jet are
insufficient
to further erode the boundary. The steady-state profile is calculated separately by
applying critical conditions along the bed surface for the incipient
motion of particles.
These conditions invoke a relationship between the mobilizing force exerted by the
jet, the weight of the particles and the local gradient of the bed. Use of the new
scaling laws for the downstream variation of the boundary shear stress then permits
the calculation of the shape of the steady-state scour pit. The
predicted profiles are
in good agreement with the experimental studies on the erosive action of submerged
water and air jets on beds of sand and polystyrene particles (Rajaratnam 1981).

The shape of the eroded boundary at intermediate times, before
the steady state is
attained, is elucidated by the application of a sediment-volume
conservation equation.
This relationship balances the rate of change of the bed elevation with the
divergence
of the flux of particles in motion. The flux of particles in motion
is given by a semi-empirical function of the amount by which the boundary
shear stress exceeds that
required for incipient motion. Hence the conservation equation may be integrated
to reveal the transient profiles of the eroded bed. There is good agreement between
these calculated profiles and experimental observations (Rajaratnam 1981).
Structures in stratified plane mixing layers and the

effects of cross-shear
Authors: ATSAVAPRANEE P. , GHARIB M.
Published: July 2002

A two-dimensional temporal mixing layer is generated in a stratified

tilting tank similar

to that used by Thorpe (1968). Extensive flow dynamics visualization is
carried out

using, for the top and bottom layers, fluids of different

densities but of the same index

of refraction. The two-dimensional density field is measured with the laser-induced

fluorescence technique (LIF). The study examines

further the classical problem of the

two-dimensional mixing layer and explores the effects of cross-shear on
a nominally

two-dimensional mixing layer, a situation widespread in complex industrial
and

natural flows. Cross-shear is another component of shear, in plane with
but

perpendicular to the main shear of the base flow,

generated by tilting the tank around a second axis.
Measurements of the temperature field of mushy
and liquid regions during solidification of aqueous ammonium chloride
Authors: SOLOMON T. H. , HARTLEY R. R.
Published: July 2002

Experiments are conducted to study the solidification from below
of aqueous
ammonium chloride. Thermochromic liquid crystal paints are used to visualize
the
temperature field simultaneously in both the liquid and the mushy layers.
In a
quasi-two-dimensional cell (thickness 10 mm), mushy-layer and boundary-layer
convection
are revealed as bumps in isotherms within and above the mushy layer, respectively.

The onset, growth and decay of these convective modes are measured by monitoring

the progression of the bumps during an experiment. The small-wavelength
boundary-layer
mode is short-lived (approximately 20–30 min), whereas the larger-wavelength

mushy-layer mode survives for several hours, dominating the flow even long
after
the growth has stopped. Experiments in a Hele-Shaw cell (thickness 2.0
mm) enable
simultaneous visualization of both the temperature field and the solid
fraction. A
coarsening mechanism is observed in which the flow spontaneously changes,
reducing
the strength of plume convection in one of the channels, and leading to
growth of
dendrites into the channel. An oscillatory convective mode is also observed,
perhaps
an indication of one of the oscillatory modes recently predicted by Chen,
Lu & Yang
(1994) and by Anderson & Worster (1995).
Effects of external flow on compositional and particle gravity currents
Authors: HALLWORTH MARK A. , HOGG ANDREW J. , HUPPERT HERBERT E.
Published: July 2002

The propagation at high Reynolds number of a heavy, two-dimensional
gravity current
of given initial volume at the base of a uniform flow is considered. An
experimental
setup is described for which a known volume of fluid is rapidly introduced
halfway
down a 9 m channel in which there is a uniform flow of water. The density
excess
of the released fluid is produced by either dissolving salt or suspending
particles in
water. The upstream and downstream propagation of the current was measured
for
different initial salt concentrations, particle sizes and concentrations.
A simple box
model for the motion of and deposit from the gravity current is constructed.
The
analytical results obtained compare well with our numerical solutions of
one-layer
and two-layer models incorporating the appropriate shallow-water equations.
Both
sets of results are in very good agreement with the experimental data.
Vortical patterns behind a tapered cylinder
oscillating transversely to a uniform flow
Authors: TECHET A. H. , HOVER F. S. , TRIANTAFYLLOU M. S.
Published: July 2002

Visualization studies of the flow behind an oscillating tapered
cylinder are performed
at Reynolds numbers from 400 to 1500. The cylinder has taper ratio 40[ratio ]1
and is
moving at constant forward speed U while being forced to oscillate
harmonically
in the transverse direction. It is shown that within the lock-in region
and above
a threshold amplitude, no cells form and, instead, a single frequency of
response
dominates the entire span. Within certain frequency ranges a single mode
dominates
in the wake, consisting of shedding along the entire span of either two
vortices per
cycle (‘2S’ mode), or four vortices per cycle
(‘2P’ mode); but within specific parametric
ranges a hybrid mode is observed, consisting of a ‘2S’

pattern along the part of the
span with the larger diameter and a ‘2P’ pattern
along the part of the span with the
smaller diameter. A distinct vortex split connects the two patterns which
are
phase-locked and have the same frequency. The hybrid mode is periodic,
unlike vortex
dislocations, and the location of the vortex split remains stable and repeatable,
within
one to two diameters, depending on the amplitude and frequency of oscillation
and
the Reynolds number.
The evolution of a localized vortex disturbance
in external shear flows. Part 2. Comparison with
experiments in rotating shear flows
Authors: MALKIEL EDWIN , LEVINSKI VLADIMIR , COHEN JACOB
Published: July 2002

The evolution of artificially generated localized disturbances
in the shape of hairpin
vortices, in laminar axisymmetric rotating shear flows, is investigated
experimentally.
The results are compared with the predictions of a theoretical model (Levinski

& Cohen 1995) with respect to the growth of such disturbances. Hairpin
vortices
were generated at the surface of the inner cylinder of an axisymmetric
Couette
apparatus, employing an injection–suction technique. The flow field
was analysed
from flow visualization using top and side views and by measurements of
the mean
and instantaneous velocity fields, carried out using laser Doppler anemometry
and
particle image velocimetry. An instability domain, within the range of
base flow
parameters where the flow is known to be linearly stable, was found. The
marginal
ratio between the angular velocities of the inner and outer cylinders beyond
which
the flow is stable to finite-amplitude localized disturbances agrees with
the theoretical
prediction based on the measured mean flow in the region of the disturbance.
The
dependence of the hairpin's inclination angle on the ratio between
the two angular
velocities is fairly well predicted by the theoretical model.
Unsteady ripple generation on steep gravity–capillary waves
Authors: JIANG LEI , LIN HUAN-JAY , SCHULTZ WILLIAM W. , PERLIN MARC
Published: July 2002

Parasitic ripple generation on short gravity waves (4 cm to 10 cm wavelengths) is
examined using fully nonlinear computations and laboratory experiments. Time-marching simulations show sensitivity of the ripple steepness to initial conditions,
in particular to the crest asymmetry. Significant crest fore–aft asymmetry and its
unsteadiness enhance ripple generation at moderate wave steepness, e.g. ka between
0.15 and 0.20, a mechanism not discussed in previous studies. The maximum ripple
steepness (in time) is found to increase monotonically with the underlying (low-frequency bandpass) wave steepness in our simulations. This is different from the sub-
or super-critical ripple generation predicted by Longuet-Higgins (1995). Unsteadiness
in the underlying gravity–capillary waves is shown to cause ripple modulation and
an interesting ‘crest-shifting’ phenomenon – the gravity–capillary wave crest and the
first ripple on the forward slope merge to form a new crest. Including boundary
layer efects in the free-surface conditions extends some of the simulations at large
wave amplitudes. However, the essential process of parasitic ripple generation is
nonlinear interaction in an inviscid flow. Mechanically generated gravity–capillary
waves demonstrate similar characteristic features of ripple generation and a strong
correlation between ripple steepness and crest asymmetry.
The influence of the downstream pressure
on the shock wave reflection phenomenon in steady flows
Authors: BEN-DOR G. , ELPERIN T. , LI H. , VASILIEV E.
Published: July 2002

The effect of the downstream pressure (defined here as the wake pressure behind the
tail of the reflecting wedge) on shock wave reflection in steady flows is investigated
both numerically and analytically. The dependence of the shock wave configurations
on the downstream pressure is studied. In addition to the incident-shock-wave-angle-induced hysteresis, which was discovered a few years ago, a new downstream-
pressure-induced hysteresis has been found to exist. The numerical study reveals that
when the downstream pressure is sufficiently high, an inverse-Mach reflection wave
configuration, which has so far been observed only in unsteady flows, can be also
established in steady flows. Very good agreement between the analytical predictions
and the numerical results is found.
Analytical and experimental investigations
of the reflection of asymmetric shock waves
in steady flows
Authors: LI H. , CHPOUN A. , BEN-DOR G.
Published: July 2002

The reflection of asymmetric shock waves in steady flows is studied both theoretically
and experimentally. While the analytical model was two-dimensional, three-dimensional edge effects influenced the experiments. In addition to regular and Mach
reflection wave configurations, an inverse-Mach reflection wave configuration, which
has been observed so far only in unsteady flows (e.g. shock wave reflection over concave
surfaces or over double wedges) has been recorded. A hysteresis phenomenon
similar to the one that exists in the reflection of symmetric shock waves has been
found to also exist in the reflection of asymmetric shock waves. The domains and
transition boundaries of the various types of overall reflection wave configurations
are analytically predicted.
Flow between time-periodically co-rotating cylinders
Authors: ERN PATRICIA , WESFREID JOSÉ EDUARDO
Published: July 2002

We consider oscillatory flows between concentric co-rotating cylinders at angular velocity
Ω(t)
= Ωm + Ωo cos ωt
as a prototype to investigate the competing effects of
centrifugal and Coriolis forces on the flow stability. We first study by flow visualization
the effect of the mean rotation Ωm on the centrifugal destabilization due to the
temporal modulation. We show that increasing the mean rotation first destabilizes
and then restabilizes the flow. The instability of the purely azimuthal basic flow
is then analysed by investigating the dynamics of the axial velocity component of
the vortex structures. Velocity measurements performed in the rotating frame of the
cylinders using ultrasound Doppler velocimetry show that secondary flow appears
and disappears several times during a flow period. Based on a finite-gap expression
for the basic flow, linear stability analysis is performed with a quasi-steady approach,
providing the times of appearance and disappearance of secondary flow in a cycle as
well as the effect on the instability threshold of the mean rotation. The theoretical
and numerical results are in agreement with experimental results up to intermediate
values of the frequency. Notably, the flow periodically undergoes restabilization at
particular time intervals.
Development and stability of gyrotactic plumes in bioconvection
Authors: GHORAI S. , HILL N. A.
Published: July 2002

Using the continuum model of Pedley, Hill & Kessler (1988) for bioconvection in
a suspension of swimming, gyrotactic micro-organisms, we investigate the existence
and stability of a two-dimensional plume in tall, narrow chambers with stress-free
sidewalls. The system is governed by the Navier–Stokes equations for an incompressible
fluid coupled with a micro-organism conservation equation. These equations are
solved numerically using a conservative finite-difference scheme. In sufficiently deep
chambers, the plume is always unstable to both varicose and meandering modes. A
linear stability analysis for an infinitely long plume predicts the growth rates of these
instabilities, explains the mechanisms, and is in good agreement with the numerical
results.
The interaction of skewed vortex pairs: a model
for blow-up of the Navier–Stokes equations
Authors: MOFFATT H. K.
Published: July 2002

The interaction of two propagating vortex pairs is considered, each pair being initially
aligned along the positive principal axis of strain associated with the other. As a
preliminary, the action of accelerating strain on a Burgers vortex is considered and the
conditions for a finite-time singularity (or ‘blow-up’) are determined. The asymptotic
high Reynolds number behaviour of such a vortex under non-axisymmetric strain,
and the corresponding behaviour of a vortex pair, are described. This leads naturally
to consideration of the interaction of the two vortex pairs, and identifies a mechanism
by which blow-up may occur through self-similar evolution in an interaction zone
where scale decreases in proportion to
(t* − t)1/2, where t* is the
singularity time. The relevance of Leray scaling in this interaction zone is discussed.
Vortex motion in shallow water with varying bottom topography and zero Froude number
Authors: RICHARDSON G.
Published: July 2002

The methods of formal matched asymptotics are used to investigate the motion of
a vortex in shallow inviscid fluid of varying depth and zero Froude number in the
limit as the vortex core radius tends to zero. To leading order the vortex is driven
by local gradients in the logarithm of the depth along an isobath (or depth contour).
A further term in the vortex velocity is calculated in which effects arising from the
global bottom topography, other vortices and the vortex core structure appear. The
evolution of the vortex core structure is then calculated. A point-vortex model is
formulated which describes the motion of a number of small vortices in terms of
the bottom topography, the inviscid flows around the vortices and their evolving
core structure. A numerical method for solving this model is discussed and finally
some numerical simulations of the motion of vortex pairs over a varying bottom
topography are presented.
Political liberalisation and the implementation of value added tax in Ghana
Authors: Osei Philip D.
Published: July 2002

This article examines an aspect of Ghana's political economy in the 1990s,
covering its transition to democracy from military dictatorship, and how this
change process impacted on its attempt to implement a value added tax
(VAT). It assesses the claim that political transition from autocracy to
democracy improves policy-making and policy outcomes. Ghana's experience of
implementing VAT typifies an inherent problem in African governance,
that of lack of adequate capacity for improved policy-making and for
the institutionalisation of inclusive politics and public accountability. The
VAT case served in the end to impose a previously absent level of public
accountability on the Ghanaian government.
The social and political construction of identities in the new South Africa: an analysis of the Western Cape Province
Authors: Cornelissen Scarlett , Horstmeier Steffen
Published: July 2002

In apartheid South African society, racial and ethnic identities were institutionally imposed. The end of apartheid has brought about the need for new identities to be created among South Africans, and for South Africans to forge a new relationship with their society and country. With this objective in mind, the national government is engaged in a process of nation-building. But in post-apartheid South African society, sub-national identities are also strongly coming to the fore. This is an empirical study of established and emerging identities in the Western Cape province, and the processes whereby these are constructed. The investigation shows two parallel flows of identity construction in the Western Cape: on the one hand, political leaders in the province attempt to foster an autonomous provincial identity; on the other, residents of the province show little evidence of strong political identities linked to the Western Cape. Instead, social identities are being constructed around residents’ local neighbourhoods and long-existing ethnic, class and racial identities. Rather than the social cohesion sought by the post-apartheid South African government, these identities point to persistent social polarisation.
LANGUAGE, NATION, AND COMMUNICATION Making a Virtue of Necessity: an overview of the English language in Nigeria by Ayo Banjo. Ibadan University Press, 1996, distributed by African Books Collective, Oxford. Pp. xi+167. $16.00/£8.95 paperback.
Authors: BRANN CONRAD MAX BENEDICT
Published: July 2002

This is the eloquent story of an arranged marriage, in the experience and judgement of an eminent Nigerian scholar of English, recording his life-long participation in the struggle over the status, standard, and stability of the language in his own nation.
Stability of ion-acoustic solitons in a multispecies plasma consisting

of non-isothermal electrons
Authors: CHAKRABORTY DEBALINA , DAS K. P.
Published: July 2002

A modified Kadomtsev–Petviashvili equation is derived for
ion-acoustic waves
in a multispecies plasma consisting of non-isothermal electrons. This equation

is used to investigate the stability of modified KdV solitons against long-wavelength

plane-wave perturbation using the small-k perturbation expansion

method of Rowlands and Infeld. It is found that modified KdV solitons are
stable.
Self-consistent EMHD penetration of a magnetic field into a plasma
Authors: CHUKBAR K. V. , IVANOV A. A. , SMIRNOV V. V.
Published: July 2002

The dynamics of a magnetic field in a plasma with dominant Hall
effect is
examined. The evolution of B in the problem is under the essential
influence of
the fluctuations in plasma density generated by ∇B2.
Solutions of two
self-consistent EMHD problems are obtained. It turns out to be possible
to obtain
analytical results with the use of small parameters. The phenomena described

here include self-similar nonlinear waves and the escape of a small-amplitude

precursor from a convective wave.
Relativistic and ponderomotive self-focusing at laser–plasma interaction
Authors: OSMAN FREDERICK , CASTILLO REYNALDO , HORA HEINRICH
Published: July 2002

The nonlinear plasma dielectric function due to relativistic electron motion is
derived. From this, one can obtain the nonlinear refractive index of the plasma
and estimate the importance of relativistic self-focusing in comparison with
ponderomotive non-relativistic self-focusing at very high laser intensities.
When the laser intensity is very high, ponderomotive self-focusing will be
dominant. However, at some point, when the oscillating velocity of the plasma
electrons becomes very large, relativistic effects will also play a role in self-focusing.
Electromagnetic wave propagation in a
chiroplasma-filled waveguide
Authors: GONG J.
Published: July 2002

A dispersion equation is derived for a cylindrical waveguide of
circular cross-section partially filled with chiroplasma. The propagation
characteristics of electromagnetic waves in the family of waveguide modes are
studied. The dispersion curves are given. It is found that the propagation
constant changes almost linearly with the chirality admittance for the
parameters that we choose, and increases with increasing filled area.
Larval stages of Chorismus tuberculatus (Decapoda: Caridea: Hippolytidae) from the south-western Atlantic Ocean
Authors: Thatje Sven , Bacardit Rosa
Published: July 2002

The present work provides a first description of three planktonic larval stages of Chorismus tuberculatus which were obtained from plankton samples collected in the south-western Atlantic during the expeditions of the RVs ‘Walther Herwig’ and ‘Shinkai Maru’ in 1978 and 1979, respectively. Three early developmental stages of C. tuberculatus are described and compared with those of the second species of this genus, C. antarcticus which is known to be distributed in the southern Atlantic Ocean and Antarctica. Both species are distinguishable by the presence/absence of supraorbital spines at the carapace, an anal spine and the exopodite on pereiopod 4. The rostrum is less developed in C. tuberculatus, the shape of the somites is less pronounced, and the number of posterior spines at the telson is lower than in C. antarcticus. Due to an abbreviated larval development as a physiological adaptation to it wider distribution into the Polar region, we assume C. antarcticus to have phylogenetically separated from C. tuberculatus, represented by the well developed first larval stages in contrast to that of the species described herein.
The occurrence of abnormal embryos in two ovoviviparous barnacle-dwelling littorinids
Authors: Johnson Lisa J. , Mill Peter J. , Hull Susan L. , Ducrotoy Jean-Paul
Published: July 2002

The occurrence of developmental abnormalities in two ovoviviparous littorinids (Littorina neglecta and a barnacle-dwelling form of L. saxatilis) inhabiting the barnacle zone at Peak Steel, Ravenscar on the north-east coast of England was investigated. In general developmental abnormalities appeared to be a rare occurrence in both taxa. However, L. neglecta was found to have a significantly greater proportion of deformed embryos in their brood pouches than L. saxatilis B (Figure 1). A distinct seasonal variation in the number of developmental abnormalities was observed in L. neglecta, and it is suggested this is a result of broods developing outside of the main reproductive season being more prone to deformity.
Cytochemical and physiological studies of the energetic metabolism and osmotrophy in Sagitta friderici (chaetognath)
Authors: Duvert Michel , Gourdoux Lucienne , Moreau Robert
Published: July 2002

Different glucidic labelled compounds were used for carbohydrate metabolism exploration, tissular glycogen storage localization and amino acid uptake response to osmotic variation in the adult of Sagitta friderici.

After [1-14C] glucose or [6-14C] glucose (osmotrophic) assimilation, the relative activity of the different metabolic pathways (glycolysis–citric acid cycle and pentose cycle) have been estimated by means of a micro-radiorespirometric method. The kinetics of expired 14CO2 showed that adult Sagitta mainly used the glycolytic–Krebs cycle rather than the pentose cycle in glucose catabolism.

After 2-deoxy-D-[1-14C] glucose (osmotrophic) assimilation, tissular glycogen storages were localized. It was shown that glycogen deposits are abundant in several tissues except the locomotor muscles, which probably represent the main glucose consumers in these very active animals. The problem of glucose transport from the storage localizations to the sites of utilization has been discussed.

The L-3H-leucine uptake variations into the Sagitta body after an osmotic shock have been estimated.