bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of pollination time, seed size, position and

maturity on quantitative variation in Nicotiana rustica
Authors: POONI H. S. , FOSTER R. , ZHAO B.
Published: July 2002

Many biological experiments and almost all quantitative genetic
studies

draw conclusions from

differences between families. Such differences are caused as much by heritable

as by non-heritable

sources. This paper investigates the impact of seed quality on the expression

of quantitative

variability among 20 highly inbred lines of Nicotiana rustica
using

ten seed categories representing

different pollination times, seed sizes, seed positions in the capsule
and seed

maturity. Analysis of

variance revealed that while the mean performance of the inbred lines remained

more or less the same

across all the seed categories, their individual performances differed
widely,

showing a highly

significant interaction between lines and seed categories. This interaction

accounted for up to 12%

of the total variation and was largely attributable to late pollinations
and

immature seed. Seed

categories were also the main source of heterogeneity among the within-line

variances, but only

immature seed lowered the correlation between the inbred means. In general,

seed quality affected the

developmental characters much less than the traits measured at or after

flowering, and the expression

of genetic variation was not critically affected by seed size or position.

Immature seed, on the other

hand, generated the highest level of unreliability in the comparative

performance of lines and such

seeds should therefore not be used in quantitative genetic experiments
under

any circumstances.

Further implications of seed quality effects on the interpretation of genetic

components are discussed in detail.
Reproductive performance, progesterone serum,
and milk production in spring postpartum Awassi
and Finn×Texel×Awassi ewes
Authors: HAMADEH S. K. , BARBOUR E. , ABI SAID M. , DAADAA K. , TARRAF C. G.
Published: July 2002

Spring postpartum reproductive performance was investigated in
19 Awassi and 15
Finn×Texel×Awassi (FTA) crossbred ewes, weaned at 2 months
postpartum and simultaneously
exposed to rams for a period of 48 days. The study was conducted in 1991/92
in the Bekaa Valley
of Lebanon.

Postpartum FTA ewes tended to have higher fecundity and prolificacy
than those of Awassi ewes.
Forty percent of the FTA ewes conceived and gave birth to 1·3 lambs
per lambing, while 31·4% of
the Awassi ewes conceived and lambed (1·1 lambs per lambing). Lambing
to lambing and ram
introduction to lambing intervals were similar in both genotypes and confirmed
that a sizeable
proportion (30–40%) of Awassi ewes and their crosses may rebreed
during spring postpartum
anoestrus and lamb at c. 8 months interval. Furthermore, relative
progesterone values revealed
continuous ovarian activity in 16% of Awassi ewes and 40% of FTA ewes and
confirmed estimates
of conception in ewes. All ewes with continuous ovulation mated and lambed.
Weekly estimates of
milk production over a 2-month period, starting the second week of lactation,
showed that daily milk
yields were almost twice as much in Awassi as in FTA ewes (P<0·01).
These results indicate the
potential for Awassi ewes and their crosses to be incorporated into frequent
lambing systems.
Reproductive efficiency in these ewes could be monitored efficiently by
measuring progesterone at 2-weekly intervals.
Proceedings of the Thirtieth Meeting of the
Agricultural Research Modellers' Group
Authors: FRANCE J.
Published: July 2002

This group, which is concerned with the applications of mathematics

to agricultural science, was formed in
1970 and has since met at approximately yearly intervals in London
for one-day meetings. The thirtieth
meeting of the group, chaired by G. J. S. Ross of the Institute of
Arable Crops Research, Rothamsted, was held
in the Wellcome Meeting Room at the Royal Society, 6 Carlton House Terrace,

London on Friday, 3 April 1998, when the following papers were read.
Long-term yield patterns in barley-based cropping systems in Northern Syria. 1. Comparison of rotations
Authors: JONES M. J. , SINGH M.
Published: July 2002

Trials, reflecting the feed needs in dry Mediterranean environments of small-ruminant production
systems based on barley, were established at two sites in Syria in 1982. They compared various 2-course rotations of barley with feed legumes, fallow or more barley. This paper summarizes a 14-year
sequence of results from an incomplete factorial combination of four rotations (B-V, B-L, B-F, B-B)
of barley with vetch (Vicia sativa), lathyrus (Lathyrus sativus), fallow, and barley, with two fertilizer
regimes, zero control and biennial NP applied to the barley phase, in terms of long-term mean yields,
production stability and yield trends over time.

On a 2-year rotational basis, most barley was produced by barley-only rotations, and differences
between B-F and B-B were small; but, in terms of total biomass production, feed legume rotations
(B-V and B-L) outyielded barley-only rotations by 29% at one site and 19% at the other. Responses
to biennial fertilization were large but did not interact significantly with rotation treatment. The crude
protein status (%N) of barley grain and straw was strongly determined by seasonal rainfall, but that
of the grain could be enhanced, irrespective of rainfall, by a preceding feed-legume crop; and,
altogether, the total mean crop nitrogen output of legume-based rotations exceeded that of barley-only rotations by 80% and 64% at the two sites. The inclusion of legumes thus enhances both
quantity and quality of feed production.

Annual yield fluctuations, attributable mainly to rainfall difference, were greater at the drier site.
No consistent effect from fertilizer was observed, but at the wetter site rotation differences were
appreciable, with B-F rotation giving the most stable yields. A number of time trends in yield values
were tentatively identified. On a relative basis, some widening over time of the gap between fertilized
and unfertilized treatments was observed in feed-legume yields at both sites and barley yields at the
wetter site; over 14 years, yields in unfertilized plots had apparently declined relative to those
receiving biennial NP. But, apart from a probable decline in lathyrus productivity compared to that
of common vetch, changes in relative yield performance between rotations were difficult to detect.
Regression models developed to describe absolute yield trends indicated a real decline over time in
barley grain yields in continuous barley (B-B) at both sites and in unfertilized plots of all four
rotations at the wetter site.
‘‘I wish you a land'': Hawai'i Short Story Cycles and aloha ′aina
Authors: DAVIS ROCÍO G.
Published: July 2002

The artistic appropriation of place ranks among the central concerns of
Asian American writing. Place in literature, a simultaneous geography of
space and imagination, has the potential to represent communal formation
and preservation as it highlights the identity that binds its members in a
shared sense of purpose and a common sense of belonging. For first-generation
writers, the portrayal of the land of the past often blends with
that of the present, offering a vivid depiction of how immigrants perceive
the physical and emotional journey from the geographic and temporal
past to the present, as they struggle to establish themselves in the new
surroundings. For second-generation Asian Americans, place often
acquires another meaning, that of a definition of self in the place of birth,
as they shift between visions of their parents' past location and their own
cultural differences. Third-generation writers engage a wide spectrum of
negotiations with the land that was a protagonists of their growing up,
and that of their increasingly complex personal and community history.
Consequently, a sense of place becomes one of the most significant
elements the Asian American writer can manipulate to condition self-representation
and the portrayal of community.
Virtual Eden: Lolita, Pornography, and the Perversions of American Studies
Authors: GILES PAUL
Published: July 2002

Native of St. Petersburg, author of works in Russian and French as well
as English, and sometime goalkeeper for Trinity College, Cambridge,
soccer team, Vladimir Nabokov would not appear to be the most obvious
avatar of American Studies in the subject's nationalist phase of the 1950s.
My argument, however, is that Lolita, which first appeared in 1955, can
be seen as symbiotically intertwined with various classic texts of American
Studies that helped to invent and define the field during the Truman and
Eisenhower years. At times, the dream of Eden that permeates Nabokov's
narrative impels it towards becoming a parody of the early American
Studies movement, which harboured within its collective consciousness
similar vestiges of an imaginary paradise. More dexterously, though,
Lolita makes the theoretical parameters of this movement visible, so that
Nabokov's novel might more accurately be described as a metafiction of
area studies: a text which holds up a mirror to the implicit assumptions
of American Studies and renders them translucent. Just as the process of
metafiction can reilluminate ways in which more traditional artefacts have
been constructed, so Nabokov's virtualization of American Studies also
reflects back upon the established boundaries of other national formations
and nation-states, foregrounding the contingent status of their supposedly
naturalized values and social markers. In particular, by focusing upon the
cultural reception of Lolita in Britain, we will see how the book brings
into play troublesome questions about the relationship between formal
aesthetics, public morality, and social power. In this sense, Nabokov's
perverse reinscription of American Studies might be seen ironically to
highlight the multiple dilemmas involved in circumscribing specific
national territories for academic study or political jurisdiction.
MEASURING EXCESS RISK OF CHILD MORTALITY: AN EXPLORATION OF DHS I FOR BURUNDI,
UGANDA AND ZIMBABWE
Authors: McMURRAY CHRISTINE
Published: July 2002

This paper proposes a new method of measuring excess risk of child
mortality in cross-sectional surveys, which is applied to DHS I data for
Burundi, Uganda and Zimbabwe. The expected child mortality experience is
estimated for each mother on the basis of child's age, mother's age at child's
birth and her parity, and compared with her observed experience. Mothers who
exceed their expected child mortality experience and also had more than one
child die are considered to have excess child mortality. Zimbabwe had the
greatest concentration of child deaths as measured by a simple ratio of
mothers to deaths, but when observed experience was compared with expected it
had less than half as many excess deaths as Uganda and Burundi. In all three
countries mother's education had a strong negative
association with the risk of excess child mortality, and in
Zimbabwe and Burundi there were significant regional differences.
THE INTERACTING EFFECTS OF PRICES AND WEATHER ON POPULATION CYCLES IN A PREINDUSTRIAL COMMUNITY
Authors: SCOTT SUSAN , DUNCAN S. R. , DUNCAN C. J.
Published: July 2002

The exogenous cycles and population dynamics of the community at Penrith, Cumbria, England, have been studied (1557-1812) using aggregative analysis, family reconstitution and time series analysis. This community was living under marginal conditions for the first 200 years and the evidence presented is of a homeostatic regime where famine, malnutrition and epidemic disease acted to regulate the balance between resources and population size. This provides an ideal historic population for an investigation of the direct and indirect effects of malnutrition. Throughout the period studied, a short wavelength oscillation in grain prices was apparently the major external factor that drove exogenous cycles in mortality, birth rate, and migration. In particular, the different responses of children to variations in food supply are emphasised; fluctuations in poor nutrition correlated significantly with the variations in mortality rates for infants (probably indirectly during pregnancy and directly during the first year of life) and for young children (via susceptibility to lethal infectious diseases). Migratory movements contributed to the maintenance of homeostasis in the population dynamics. A medium wavelength cycle in low winter temperatures was associated with a rise in adult mortality which, in turn, promoted an influx of migrants into this saturated habitat. A model incorporating these interacting associations between vital events and exogenous cycles is presented: grain prices were an important density-dependent factor and constituted the major component of the negative feedback of this population and drove the exogenous, short wavelength mortality cycles. Cycles of births and immigration provide a positive feedback for the build-up of susceptibles and the initiation of smallpox epidemics and increased population size.
Effect of partial hydrolysis with an immobilized proteinase on thermal gelation properties of β-lactoglobulin B
Authors: OTTE JEANETTE , LOMHOLT STIG B. , IPSEN RICHARD , QVIST KARSTEN B.
Published: July 2002

We have investigated the influence of partial hydrolysis with an
immobilized proteinase from Bacillus licheniformis on the thermal gelation of
isolated β-lactoglobulin B. Gelation behaviour was determined by dynamic
rheological measurements (small deformation) and the gels were characterized with
respect to microstructure and water-holding properties. A fine-stranded gel with a
complex modulus of ∼ 2000 Pa was formed from β-lactoglobulin (50 g/l in 75 mM-Tris-HCl,
pH 7·5). Limited hydrolysis prior to thermal gelation resulted in coarser
gels with thicker protein strands and larger pores. Gel structure correlated with its
permeability, proton mobility and water-holding capacity. Total gel stiffness
increased with low degrees of hydrolysis, but decreased after prolonged hydrolysis.
Maximal gel stiffness was 1·5-fold that of gels made from unhydrolysed
β-lactoglobulin. This was much lower than the stiffening effect obtained after partial
hydrolysis of whey protein isolate, showing that the gel strengthening effect of
partial hydrolysis was dependent on the protein composition and/or the hydrolysis
and gelation conditions. A mechanism to explain the observed effects of hydrolysis
on gelation and gel properties is presented.
Accelerated ripening of Pecorino Umbro cheese
Authors: CORSETTI ALDO , GOBBETTI MARCO , SMACCHI EMANUELE , DE ANGELIS MARIA , ROSSI JONE
Published: July 2002

We have investigated accelerating the ripening of Pecorino Umbro
cheese
by adding crude cytoplasmic extract from Pseudomonas fluorescens,
non-starter
lactic acid bacteria (NSLAB) or cheese slurry. Microbiological and biochemical
analyses and sensory evaluation were carried out on control and experimental
cheeses over 28 d ripening. In the cheeses containing NSLAB or slurry,
counts of
mesophilic lactobacilli ranged from log 7·6 at day 1 to ∼log
8·6 cfu/g after 28 d
ripening, ∼2 log cycles higher than in the control cheese. All the
experimental
cheeses contained higher levels than the control of total free amino acids
and N
soluble at pH 4·6 and in 120 g trichloroacetic acid/l. Compared
with the control,
higher aminopeptidase and dipeptidase activities were found in the cheeses
containing NSLAB and slurry, and especially in those containing the Pseudomonas
enzyme. The cheeses containing NSLAB or slurry were characterized by an
accumulation of short peptides (Mr<2000)
detected by FPLC. Although the cheese
containing enzyme had an atypical flavour, the addition of mesophilic lactobacilli
reduced from 60 to 28 d the ripening period of Pecorino Umbro cheese, without
the
appearance of off flavour.
Edmund Dudley and the Church
Authors: GUNN STEVEN
Published: July 2002

Edmund Dudley, minister of Henry VII, was a man both personally
extraordinary and yet representative of his age. He abandoned the
normal cursus honorum of the legal profession to enter the king's
service more suddenly than any of his contemporaries; yet he was one of
many common lawyers newly influential in the king's councils of the later
fifteenth and earlier sixteenth centuries. He was probably the only layman
in Henry's inner circle to have studied at a university; yet within fifty
years of his death most English statesmen of the first rank would have
done so. In pursuing the king's interests, Dudley generated sufficient
animosity to make himself one of the two scapegoats for Henry's policies
tried and executed in 1509–10; yet it was more his manner, his efficiency
and his political isolation than any difference of intent that distinguished
him from Henry's other ministers. In pursuing his own interests he built
a large landed estate faster than any of his colleagues, but their aims and
eventual achievements were not so different from his. The one respect in
which Dudley was unique was that he had leisure, while under arrest in
the Tower of London, to commit to paper his thoughts on English
government and society. The resulting treatise, The tree of commonwealth,
enables us to juxtapose his stated ideals with his actions as a royal minister
and as an influential layman. Thereby we may hope to shed new light on
the relations between Church, State and lay elites on the eve of the
English Reformation.
Internal wave evolution in a space–time varying field
Authors: HORN D. A. , REDEKOPP L. G. , IMBERGER J. , IVEY G. N.
Published: July 2002

An extended Korteweg–de Vries (KdV) equation is derived that describes the evolution
and propagation of long interfacial gravity waves in the presence of a strong, space–time
varying background. Provision is made in the derivation for a spatially varying
lower depth so that some topographic effects can also be included. The extended
KdV model is applied to some simple scenarios in basins of constant and varying
depths, using approximate expressions for the variable coefficients derived for the case
when the background field is composed of a moderate-amplitude ultra-long wave. The
model shows that energy can be transferred either to or from the evolving wave packet
depending on the relative phases of the evolving waves and the background variation.
Comparison of the model with laboratory experiments confirms its applicability and
usefulness in examining the evolution of weakly nonlinear waves in natural systems
where the background state is rarely uniform or steady.
Turbulent flow between a rotating and a stationary disk
Authors: LYGREN MAGNE , ANDERSSON HELGE I.
Published: July 2002

Turbulent flow between a rotating and a stationary disk is studied. Besides its fundamental
importance as a three-dimensional prototype flow, such flow fields are frequently
encountered in rotor–stator configurations in turbomachinery applications. A
direct numerical simulation is therefore performed by integrating the time-dependent
Navier–Stokes equations until a statistically steady state is reached and with the
aim of providing both long-time statistics and an exposition of coherent structures
obtained by conditional sampling. The simulated flow has local Reynolds number
r2ω/v = 4 × 105
and local gap ratio s/r = 0.02, where ω is the angular velocity of the
rotating disk, r the radial distance from the axis of rotation, v the kinematic viscosity
of the fluid, and s the gap width.

The three components of the mean velocity vector and the six independent Reynolds
stresses are compared with experimental measurements in a rotor–stator flow configuration.
In the numerically generated flow field, the structural parameter a1 (i.e. the
ratio of the magnitude of the shear stress vector to twice the mean turbulent kinetic
energy) is lower near the two disks than in two-dimensional boundary layers. This
characteristic feature is typical for three-dimensional boundary layers, and so are the
misalignment between the shear stress vector and the mean velocity gradient vector,
although the degree of misalignment turns out to be smaller in the present flow than
in unsteady three-dimensional boundary layer flow. It is also observed that the wall
friction at the rotating disk is substantially higher than at the stationary disk.

Coherent structures near the disks are identified by means of the λ2 vortex criterion
in order to provide sufficient information to resolve a controversy regarding the roles
played by sweeps and ejections in shear stress production. An ensemble average of
the detected structures reveals that the coherent structures in the rotor–stator flow are
similar to the ones found in two-dimensional flows. It is shown, however, that the three-dimensionality of the mean flow reduces the inter-vortical alignment and the tendency
of structures of opposite sense of rotation to overlap. The coherent structures near the
disks generate weaker sweeps (i.e. quadrant 4 events) than structures in conventional
two-dimensional boundary layers. This reduction in the quadrant 4 contribution from
the coherent structures is believed to explain the reduced efficiency of the mean flow
in producing Reynolds shear stress.
Steady-state flows in an enclosure ventilated by buoyancy forces assisted by wind
Authors: HUNT G. R. , LINDEN P. F.
Published: July 2002

We examine ventilation driven by a point source of buoyancy on the floor of an
enclosure in the presence of wind. Ventilation openings connecting the internal and
external environment are at high level on the leeward façade and at low level on the
windward façade, so that the wind-driven flow in the enclosure is in the same sense
as the buoyancy-driven flow. We describe laboratory experiments that determine the
parameters controlling the ventilation under these conditions and compare the results
with predictions of a theoretical model.

Previous work has shown that when ventilation is driven solely by a single localized
source of buoyancy flux B, a stable, two-layer stratification and displacement flow
forms. The steady height of the interface, between the buoyant upper layer and the
lower layer at ambient density ρ, is independent of B and depends only on the
‘effective’ area A* of the openings, the height H of the enclosure and entrainment into
the plume.

For wind-assisted flows, the ventilation is increased owing to the wind pressure
drop δ between the windward and leeward openings. The two-layer stratification
and displacement flow are maintained over a range of wind speeds, even when the
wind-induced flow far exceeds the flow induced by the buoyancy force. The steady
height of the interface depends upon the Froude number
Fr = (Δ/ρ)1/2(H/B)1/3 and
the dimensionless area of the openings A*/H2. Increasing the wind speed raises the
position of the interface and decreases the temperature of the upper layer (as does
increasing A*/H2), while increasing B lowers the level of the interface and increases
the temperature of the upper layer. For significantly larger Fr, the displacement flow
breaks down and we investigate some aspects of this breakdown. The implications of
these flows to passive cooling of a building by natural ventilation are discussed.
Instability caused by the coupling between

non-resonant shape oscillation modes of a

charged conducting drop
Authors: FENG Z. C.
Published: July 2002

By examining the modal interaction between two non-resonant

shape oscillation modes of a charged liquid drop, we have

identified a new route to instability via nonlinear coupling.

We present numerical simulation results to show that when shape

perturbation of a high-mode number Legendre mode is applied

to the drop, the prolate–oblate mode of the drop may grow

unbounded. Using multiple-scale analysis, we derive amplitude

equations for the high-mode-number shape mode and the

prolate–oblate mode to show the nonlinear coupling between

the two modes.
A composite asymptotic model for the wave motion in a steady
three-dimensional subsonic boundary layer
Authors: RYZHOV OLEG S. , TERENT'EV EUGENE D.
Published: July 2002

The problem for a thin near-wall region is reduced, within the triple-deck
approach,
to unsteady three-dimensional nonlinear boundary-layer equations subject to an
interaction law. A linear version of the boundary-value problem describes eigenmodes
of different nature (including crossflow vortices) coupled together. The
frequency ω
of the eigenmodes is connected with the components k and m of
the wavenumber
vector through a dispersion relation. This relation exhibits two singular properties.
One of them is of basic importance since it makes the imaginary part Im(ω)
of the
frequency increase without bound as k and m tend to infnity
along some curves in
the real (k, m)-plane. The singularity turns out to be
strong, rendering the Cauchy problem ill posed for linear equations.

Accounting for the second-order approximation in asymptotic expansions for the
upper and main decks brings about significant alterations in the interaction law. A
new mathematical model leans upon a set of composite equations without rescaling
the original independent variables and desired functions. As a result, the
right-hand
side of a modified dispersion relation involves an additional term multiplied
by a small
parameter ε=R−1/8, R being the
reference Reynolds number. The aforementioned
strong singularity is missing from solutions of the modified dispersion
relation. Thus,
the range of validity of a linear approximation becomes far more extended
in ω, k
and m, but the incorporation of the higher-order term into the
interaction law means
in essence that the Reynolds number is retained in the formulation of a key problem
for the lower deck.
The pressure drop created by a ball settling in a

quiescent suspension of comparably sized spheres
Authors: MONDY L. A. , TETLOW N. , GRAHAM A. L. , ABBOTT J. , BRENNER H.
Published: July 2002

Measurements are reported of the pressure differences ΔP

existing at large distances

above and below a ball settling along the axis of a circular cylinder filled
with an

otherwise quiescent viscous Newtonian liquid in which identical particles,
comparable

in size to the settling ball, are suspended. The suspensions ranged in
solids volume

fraction ϕ from 0.30 to 0.50 and consisted of 0.635 cm diameter spheres

density-matched to the suspending oil. The settling balls varied in diameter
from

0.318 to 1.27 cm, resulting in particle Reynolds numbers always less than
about

0.4 based upon

ball diameter and the effective viscosity of the suspension. For the moderately

concentrated suspension (ϕ=0.30), the product of ΔP
with

the cross-sectional area A

of the containing cylinder was observed to be equal to twice the drag force

D on the

settling sphere, in accord with theory. In the more concentrated suspension

(ϕ=0.50) this product was found to be slightly, but significantly,
less

than twice the drag on the

settling sphere. It is speculated that this lower pressure drop may result
from the

presence of one or more of the following phenomena: (i) migration of the
falling ball

off the cylinder axis ; (ii) apparent slip of the suspension at

the cylinder wall; (iii)

blunting of the otherwise Poiseuillian parabolic velocity profile, the

latter phenomenon

being known to occur during the creeping flow of concentrated suspensions
through

circular tubes. Incidental to the suspension experiments, for a homogeneous
fluid we

verify the classical theoretical formula for the off-axis

pressure drop when the sphere

settles at a non-concentric position in the cylinder.
Experiments on collapsing turbulent regions in stratified fluids
Authors: DE SILVA I. P. D. , FERNANDO H. J. S.
Published: July 2002

Laboratory experiments were carried out to investigate the properties
of a collapsing
turbulent patch generated within a linearly stratified fluid by a sustained
energy source
and its long-time evolution in the presence of lateral boundaries. An oscillating
grid
spanning the width of the experimental tank was used as the turbulence
source.
Initially, the patch grows rapidly, as in an unstratified fluid, until
the buoyancy forces
arrest its vertical growth. Thereafter, the patch collapses to form horizontally

propagating intrusions at its equilibrium density level. The fluid lost
from the patch
into the intrusion is replenished by return currents generated at the top
and bottom
edges of the patch. The nose of the intrusion propagates with a constant
average speed
(‘initial spreading regime’) determined mainly by the horizontal
pressure gradient
forces and the resistance induced by upstream propagating, low-frequency,
columnar
internal waves. Although the intrusion propagation speed is independent
of viscous
effects, they cause the development of a slug of fluid pushed ahead of
the intrusion.
When this slug reaches the endwall, strong upstream blocking occurs, causing
the
intrusion to decelerate (‘blocked regime’); the
intrusion nose, however, eventually
reaches the endwall. The thickness of the patch is found to be approximately
constant
during the initial spreading regime and slowly growing in the blocked regime.
At large
times (t) both the patch and the ‘fully blocked’
intrusion begin to grow vertically with
a power law of the form t1/5. A simple
mixing model is advanced to explain this
observation. Various turbulent and internal-wave parameters pertinent to
collapsing
patches were also measured, and their properties were compared with
those of non-collapsing patches.
An approximation for the highest gravity waves on water of finite
depth
Authors: KARABUT E. A.
Published: July 2002

Planar steady gravity waves of finite amplitude at the surface
of an ideal
incompressible fluid above a flat bottom are studied theoretically. A new
approach to
the construction of some steady flows of heavy fluid with a partially free
surface
is proposed. The hypothesis is suggested and justified that these flows
are close to
gravity waves. For the case of the highest waves a one-parameter family
of exact
solutions describing free boundary flows above a flat bottom and under
two uneven
symmetrically located caps is derived. This family of solutions gives an
approximation
to the highest water waves in moderate to shallow water depths, enabling
relatively
simple calculation of their properties.
Experimental study of the fine-scale structure of
conserved scalar mixing in turbulent shear flows.
Part 2. Sc≈1
Authors: BUCH KENNETH A. , DAHM WERNER J. A.
Published: July 2002

Results are presented from an experimental study into the fine-scale
structure of
generic, Sc≈1, dynamically passive, conserved scalar fields

in turbulent shear flows.
The investigation was based on highly resolved, two-dimensional imaging
of laser
Rayleigh scattering, with measurements obtained in the self-similar far
field of an
axisymmetric coflowing turbulent jet of propane issuing into air at local
outer-scale
Reynolds numbers Reδ≡uδ/v

of 11000 and 14000. The resolution and signal quality
of these measurements allowed direct differentiation of the scalar field
data
ζ(x, t) to
determine the instantaneous scalar energy dissipation rate field
(Re Sc)−1∇ζ·∇ζ(x,
t).
Results show that, as for large-Sc scalars (Buch & Dahm 1996),

the scalar dissipation
rate field consists entirely of strained, laminar, sheet-like diffusion
layers, despite the
fact that at Sc≈1 the scale on which these layers are folded

by vorticity gradients is
comparable to the layer thickness. Good agreement is found between the
measured
internal structure of these layers and the self-similar local solution
of the scalar
transport equation for a spatially uniform but time-varying strain field.
The self-similar
distribution of dissipation layer thicknesses shows that the ratio of maximum
to
minimum thicknesses is only 3 at these conditions. The local dissipation
layer thickness
is related to the local outer scale as
λD/δ
≡ΛRe−3/4δSc−1/2, with the average thickness
found to be 〈Λ〉=11.2, with both the largest
and smallest layer thicknesses following Kolmogorov
Re−3/4δ) scaling.
Investigation of thermocapillary convection in a three-liquid-layer system
Authors: GÉORIS Ph. , HENNENBERG M. , LEBON G. , LEGROS J. C.
Published: July 2002

This paper presents the first experimental results on Marangoni–Bénard instability
in a symmetrical three-layer system. A pure thermocapillary phenomenon has been
observed by performing the experiment in a microgravity environment where buoyancy
forces can be neglected. This configuration enables the hydrodynamic stability
of two identical liquid–liquid interfaces subjected to a normal gradient of temperature
to be studied. The flow is driven by one interface only and obeys the criterion
based on the heat diffusivity ratio proposed by Scriven & Sternling (1959) and Smith
(1966). The measured critical temperature difference for the onset of convection is
compared to the value obtained from two-dimensional numerical simulations. The
results of the simulations are in reasonable agreement with the velocimetry and the
thermal experimental data for moderate supercriticality. Numerically and experimentally,
the convective pattern exhibits a transition between different convective regimes
for similar temperature gradients. Their common detailed features are discussed.
Experimental studies of strongly stratified flow past three-dimensional orography
Authors: VOSPER S. B. , CASTRO I. P. , SNYDER W. H. , MOBBS S. D.
Published: July 2002

Stably stratified flows past three-dimensional orography have been investigated using
a stratified towing tank. Flows past idealized axisymmetric orography in which the
Froude number, Fh=U/Nh
(where U is the towing speed, N is the buoyancy
frequency and h is the height of the obstacle) is less than unity have been studied.
The orography considered consists of two sizes of hemisphere and two cones of
different slope. For all the obstacles measurements show that as Fh decreases, the
drag coefficient increases, reaching between 2.8 and 5.4 times the value in neutral flow
(depending on obstacle shape) for Fh[les ]0.25. Local maxima and minima in the drag
also occur. These are due to the finite depth of the tank and can be explained by linear
gravity-wave theory. Flow visualization reveals a lee wave train downstream in which
the wave amplitude is O(Fhh), the smallest wave amplitude occurring for the steepest
cone. Measurements show that for all the obstacles, the dividing-streamline height,
zs, is described reasonably well by the formula
zs/h=1−Fh. Flow visualization
and acoustic Doppler velocimeter measurements in the wake of the obstacles show
that vortex shedding occurs when Fh[les ]0.4 and that the period of the vortex
shedding is independent of height. Based on velocity measurements in the wake of
both sizes of hemisphere (plus two additional smaller hemispheres), it is shown that a
blockage-corrected Strouhal number, S2c
=fL2/Uc, collapses onto a single curve when
plotted against the effective Froude number,
Fhc=Uc/Nh. Here, Uc is the blockage-corrected free-stream speed based on mass-flux considerations, f is the vortex shedding
frequency and L2 is the obstacle width at a height
zs/2. Collapse of the data is also
obtained for the two different shapes of cone and for additional measurements made
in the wake of triangular and rectangular at plates. Indeed, the values of
S2c for all
these obstacles are similar and this suggests that despite the fact that the obstacle
widths vary with height, a single length scale determines the vortex-street dynamics.
Experiments conducted using a splitter plate indicate that the shedding mechanism
provides a major contribution to the total drag (∼25%). The addition of an upstream
pointing ‘verge region’ to a hemisphere is also shown to increase the drag significantly
in strongly stratified flow. Possible mechanisms for this are discussed.
The second-law analysis of convective pattern
change in a rectangular cavity
Authors: NARUSAWA UICHIRO
Published: July 2002

Natural convection in a rectangular cavity is examined, utilizing the second law of thermodynamics. Through an application of the second law the rate of entropy
generation associated with the convective pattern changes is evaluated for the onset
of natural convection in a cavity with free boundaries, for which an exact solution
is sought, as well as with rigid boundaries which is studied numerically. Entropy to
be generated from the perturbed temperature and velocity fields is shown to depend
on AR (aspect ratio of the cavity), Rac
(the critical Rayleigh number) and a non-dimensional parameter, Ω, which is related to the ratio of entropy generation by
viscous friction to that by thermal transport. The convective pattern change is related
to a change in the spatial distributions of the rate of entropy generation due to heat
transfer and due to dissipation, demonstrating that an application of the second law
helps examine convective pattern changes quantitatively by dealing with temperature
and velocity fields in a unified manner.
A resonant wave theory
Authors: YAO LUN-SHIN
Published: July 2002

Analysis is used to show that a solution of the Navier–Stokes equations can be
computed in terms of wave-like series, which are referred to as waves below. The
mean flow is a wave of infinitely long wavelength and period; laminar flows contain
only one wave, i.e. the mean flow. With a supercritical instability, there are a mean
flow, a dominant wave and its harmonics. Under this scenario, the amplitude of the
waves is determined by linear and nonlinear terms. The linear case is the target
of flow-instability studies. The nonlinear case involves energy transfer among the
waves satisfying resonance conditions so that the wavenumbers are discrete, form a
denumerable set, and are homeomorphic to Cantor's set of rational numbers. Since
an infinite number of these sets can exist over a finite real interval, nonlinear
Navier–Stokes equations have multiple solutions and the initial conditions determine
which particular set will be excited. Consequently, the influence of initial conditions can
persist forever. This phenomenon has been observed for Couette–Taylor instability,
turbulent mixing layers, wakes, jets, pipe flows, etc. This is a commonly known
property of chaos.
Note on a paper by Ogilvie:
the interaction between waves and
a submerged horizontal cylinder
Authors: ARENA F.
Published: July 2002

Ogilvie (1963) obtained the solution for the interaction between gravity waves and
a horizontal submerged circular cylinder on deep water. It is shown herein that in
this solution the expressions for the velocity potential (both for the moving cylinder
and for the fixed cylinder) lack one term: a time-periodic space-independent term,
which does not modify the load, but has some important consequence on the pressure
distribution.
The singular perturbation of surface tension in Hele-Shaw flows
Authors: CENICEROS HECTOR D. , HOU THOMAS Y.
Published: July 2002

Morphological instabilities are common to pattern formation problems such as the
non-equilibrium growth of crystals and directional solidification. Very small perturbations
caused by noise originate convoluted interfacial patterns when surface tension is
small. The generic mechanisms in the formation of these complex patterns are present
in the simpler problem of a Hele-Shaw interface. Amid this extreme noise sensitivity,
what is then the role played by small surface tension in the dynamic formation and
selection of these patterns? What is the asymptotic behaviour of the interface in the
limit as surface tension tends to zero? The ill-posedness of the zero-surface-tension
problem and the singular nature of surface tension pose challenging difficulties in
the investigation of these questions. Here, we design a novel numerical method that
greatly reduces the impact of noise, and allows us to accurately capture and identify
the singular contributions of extremely small surface tensions. The numerical method
combines the use of a compact interface parametrization, a rescaling of the governing
equations, and very high precision. Our numerical results demonstrate clearly that the
zero-surface-tension limit is indeed singular. The impact of a surface-tension-induced
complex singularity is revealed in detail. The singular effects of surface tension are
first felt at the tip of the interface and subsequently spread around it. The numerical
simulations also indicate that surface tension defines a length scale in the fingers
developing in a later stage of the interface evolution.
‘Acts of Grace’: Portuguese Monarchs
and their Subjects of African Descent
in Eighteenth-Century Brazil
Authors: RUSSELL-WOOD A. J. R.
Published: July 2002

This article examines direct appeals to Portuguese monarchs and how
this extrajudicial option was invoked by slaves and free persons of African
descent in colonial Brazil. It also addresses the production and content of appeals
and what these reflect of the lives of Afro-Brazilians, relations between slave and
owner, manumissions, judicial and individual abuse of women and popular
perceptions and expectations of a monarch. The pros and cons of this appellate
recourse are discussed in the context of colonial governance and of how royal acts
of private justice reinforced the moral authority of monarchs, the sacred quality
of monarchy and those personal qualities of magnanimity and compassion
associated with the ideal of kingship.
New Federalism, Intra-governmental Relations and Co-governance in
Mexico
Authors: WARD PETER M. , RODRÍGUEZ VICTORIA E.
Published: July 2002

Evidence from six Mexican states is analyzed about changes in
government organisation and performance arising from decentralisation and the
recasting of federalism structures. Spurred by rising pluralism, greater electoral
transparency, alternancia, and willingness of the Centre to ‘let go’,
a more genuine structure of shared powers is emerging between the executive (governors), the
legislature and the judiciary. The government bureaucracy is undergoing
modernisation, and governors are seeking to share power with legislatures as a
means of sharing the responsibilities of statecraft. Local congresses are exercising
greater ‘checks’ and ‘balances’ vis-à-vis the executive branch. Finally, the
judiciary is beginning to be reorganised, particularly at the national (Supreme
Court) level, where it is starting to develop jurisprudence relating to inter- and
intra-governmental relations.
Syllable asymmetries in comparative Yoruba phonology
Authors: ORIE OLANIKE OLA
Published: July 2002

Syllables display symmetrical and asymmetrical properties in two Yoruba dialects. In
the asymmetrical dialect, only a vowel with an onset participates in syllable-conditioned processes; an onsetless vowel is syllabically inert. In the symmetrical
dialect, a vowel, with or without an onset, participates in syllable processes. It is
argued that onsetless vowels are not syllabified in the asymmetrical dialect. Since
there is no phonological contrast between syllables with onsets and those without
onsets in the symmetrical dialect, all vowels are parsed into syllables exhaustively.
Using ideas from Optimality Theory, attested interdialectal variation is shown to
follow from different rankings of the same syllable and faithfulness constraints.
Towards a solution to violence in Burundi: a case for political and economic liberalisation
Authors: Ndikumana Léonce
Published: July 2002

The causes of violence in Burundi are complex and go beyond the alleged
‘age-old’ animosities between the Hutu and the Tutsi. In the short run, it
may be impossible to eradicate conflicts; but it is imperative to transform
conflicts into non-violent ‘shocks of ideas’ between rival parties, which must
refocus their energy at finding a negotiated settlement. This article posits that
the solution to violence must revolve around political and economic liberalisation
aimed at (1) eradicating the tradition of using the state for
oppression and accumulation; (2) achieving egalitarian development; and
(3) protecting the rights of all citizens.
Democratic reform, transition and consolidation: evidence from Senegal's 2000 presidential election
Authors: Vengroff Richard , Magala Michael
Published: July 2002

What lessons on the broad issue of successful democratic transitions and consolidation
can be drawn from the Senegalese experience? The most import
ant inference from this case is that transition is a function not of one factor
alone, or even one dominant factor, but a combination of dynamic changes
including institutional design and modification, and the attitudes, values and
beliefs of the population. In Senegal, modernisation and political culture
change activated a movement towards the transition that only became possible
as a result of institutional modifications. Institutional reform creates opportunities
but does not ensure a successful transition. The issues of social
capital, materialism/post-materialism, education, economic security, regime
performance, value change, and confidence in institutions in general all come
into play to varying degrees. The gradual creation of democratic institutions
precedes and contributes to political culture change, independent of economic
development. The article draws on survey data, a replication of the
world values survey conducted in Senegal, and an analysis of institutional
(electoral system) reforms over the last twenty-five years, with comparative
data from other African countries.
Parametric decay of an upper-hybrid wave in a
plasma cylinder
Authors: SHARMA S. C.
Published: July 2002

A large-amplitude upper-hybrid wave in a plasma cylinder is susceptible
to
parametric decay into a lower-hybrid wave and an upper-hybrid wave. The
perpendicular and parallel motions of electrons play equally important
roles in
the nonlinear interaction. The coupled-mode equations are solved using
a
perturbation technique. The growth rate of the instability is less sensitive
to the
radial mode number of the sideband. However, for higher-order radial modes
it
falls off as the overlap of the interacting wave functions decreases.
Effect of plasma flow on the equilibrium of an axisymmetric toroidal
magnetic trap
Authors: ANDRUSHCHENKO ZH. N. , CHEREMNYKH O. K. , EDENSTRASSER J. W.
Published: July 2002

The effect of finite plasma rotation on the equilibrium of an axisymmetric
toroidal magnetic trap is investigated. The nonlinear vector equations
describing the equilibrium of a highly conducting, current-carrying plasma
are
reduced to a set of scalar partial differential equations. Based on Shafranov's
well-known tokamak model, this set of equations is employed for the description
of a kinetic (stationary) plasma equilibrium. Analytical expressions for
the
Shafranov shift Δ are found for the case of finite plasma rotation,
where two
regions of possible plasma equilibria are found corresponding to sub- and
super-Alfvénic poloidal rotation. The shift Δ itself,
however, turns out to depend
essentially on the toroidal rotation only. It is shown that in the case
of a
stationary plasma flow, the solution of the Grad–Shafranov equation
is at the
same time also the solution of the stationary Strauss equation.
The effect of neutral-gas friction on
Alfvén surface waves propagating along a
plasma–vacuum interface
Authors: KUMAR NAGENDRA , SRIVASTAVA KRISHNA M.
Published: July 2002

The effect of neutral-gas friction on Alfvén surface waves
propagating along an
infinitely conducting viscous plasma–vacuum interface has been investigated.

A dispersion relation is obtained for such waves. For different values
of the
neutral-gas friction parameter
S=νc/ω (where νc
is the collisional frequency
between two components of the composite plasma), the variations of the
real
and imaginary parts kr and ki
of the wavenumber k with the viscosity parameter
vp=
μlω/ρ01v2A1

(where μl and ρ01 are the coefficient of viscosity
and
the density of plasma media 1) are shown graphically. It is concluded that
a
three-mode structure of Alfvén surface waves results flowing to
neutral-gas
friction. It is suggested that our results are useful for both laboratory
and
astrophysical plasmas (e.g. photospheres, chromospheres and cool interstellar

clouds).