bluuebunny/crossref_metadata_2025 huggingface dataset:
Interactions between heat stress and nutrition in sheep
fed roughage diets
Authors: DIXON R. M. , THOMAS R. , HOLMES J. H. G.
Published: July 2002

Intake, digestion and growth were examined in young Merino×Border Leicester wether sheep held
for 44 days in either cool (13–15°C, thermal humidity index 56–58) or
hot (32–40°C, 50–70% relative
humidity, thermal humidity index minimum 83–84, maximum 83–88) environments. The sheep were
offered diets of medium quality hay ad libitum alone (Con) or supplemented with either 22 g air-dry/kg metabolic liveweight (W0·75) of barley grain
fortified with urea and sulphur (Bar/N) or 10 g air-dry/kg W0·75
of fishmeal (FM). Intake of the Con diet by the sheep in the cool environment was
high at 79 g DM/kg W0·75
per day. Sheep in the hot environment had higher rectal temperatures and
higher respiration rates (40·1°C v. 39·2°C,
196 v. 56 respirations/min respectively, P<0·01). The hot
environment reduced (P<0·05) total dry matter (DM) intake,
estimated metabolizable energy (ME)
intake, liveweight (LW) gain and nitrogen (N) balance. The provision of supplements did not change
total DM intake, but increased (P<0·05) organic matter digestibility, estimated ME intake, LW gain
and N balance. Wool growth was increased much more by the FM than by the Bar/N supplement,
indicating that the supply of absorbed amino acids was increased substantially by the FM
supplement. Neither voluntary intake nor productivity were influenced by any interactions between
the thermal environments and the balance of nutrients provided by the diets. In conclusion, in these
young sheep consuming a high intake of a medium quality roughage diet, moderate heat stress
reduced intake and growth but did not affect the relative responses of the sheep to supplements
providing principally fermentable ME or a similar amount of fermentable ME and additional
metabolizable protein.
Effect of growth path and breed on the calpain system
in steers finished in a feedlot
Authors: THOMSON B. C. , MUIR P. D. , DOBBIE P. M.
Published: July 2002

This experiment examined the effect of feeding a concentrate diet ad libitum for two periods of time
in two breeds of contrasting mature size cattle, on the activity of the components of the calpain system
and the association between components of the calpain system and tenderness as determined by shear
force in the longissimus muscle. Nine-month-old Angus and Simmental steers were either fed ad
libitum on a feedlot from 9 months of age (F9) or on pasture until 25 months of age (F25) and then
fed on the same ad libitum ration as the F9 steers. Groups within a breed were killed at mean
liveweights of c. 800 kg for the Angus and 950 kg for the Simmental. Steers were slaughtered in a
commercial abattoir and muscle samples collected from the longissimus muscle at the 13th rib within
60 min of slaughter. The activities of the components of the calpain system were determined 2 and
24 h post-slaughter. The length of time on the feedlot diet had the largest effect on shear force of the
longissimus muscle and the activity of μ-calpain. The steers growing fastest prior to slaughter (F25)
had the highest μ-calpain activities two h post-slaughter and produced the most tender meat, even
though they were slightly older at slaughter. The best component of the calpain system for predicting
shear force over all the treatments was the activity of calpastatin 24 h post-slaughter. This association
between shear force 21 days post-slaughter and the activity of calpastatin 24 h post-slaughter was
weak and varied between the treatments. The strongest associations occurred in the F9 Angus steers
who also had the toughest meat and the slowest growth rates prior to slaughter.
The modification of an in vitro gas production test to
detect roughage related differences in in vivo microbial
protein synthesis as estimated by the excretion of
purine derivatives
Authors: BLÜMMEL M. , MGOMEZULU R. , CHEN X. B. , MAKKAR H. P. S. , BECKER K. , ØRSKOV E. R.
Published: July 2002

The relationship between variations in in vitro microbial biomass production and microbial protein
supply to the host animal was examined in 13 Malawian goats fed on stover leaves from two varieties
of maize at Bunda College, Malawi, in 1995. The in vitro parameters were analysed based on the
concept of the partitioning factor (PF) which is obtained by the combination of gas volume
measurements with determinations of the amount of substrate truly degraded. The PF reflects
substrate-dependent variation in the in vitro partitioning of degraded substrate between short chain
fatty acids (SCFA), gases and microbial biomass. The in vivo microbial protein synthesis was
estimated by the urinary excretion of the purine derivatives (PD) allantoin, uric acid and xanthine +
hypoxanthine. For the two types of stover leaves examined, the higher microbial efficiency of one
variety in vitro was reflected by different PD excretions on practically identical digestible dry matter
intakes in vivo. It is concluded that substrate-dependent variations in microbial efficiencies as detected
by the PF are also evident and relevant for in vivo microbial protein synthesis.
Effect of foliar application of Azotobacter,
Azospirillum and Beijerinckia on leaf yield and quality
of mulberry (Morus alba)
Authors: SUDHAKAR P. , CHATTOPADHYAY G. N. , GANGWAR S. K. , GHOSH J. K.
Published: July 2002

A field experiment was conducted for two years (1994–96) to evaluate three nitrogen fixing bacteria
(NFBs) namely Azotobacter, Azospirillum and Beijerinckia as foliar biofertilizers on mulberry (Morus
spp.). Foliar application of these bacteria in their specific culture media with half of the recommended
dose of N as a basal application of chemical fertilizer were compared with the recommended dose of
N (300 kg/ha per year in four equal splits) but without biofertilizer. Other controls for comparison
were respective culture media with half N. All the NFBs improved leaf yield over their respective
controls (specific culture media). The addition of Azotobacter resulted in significantly greater yield
than that given by the recommended dose of N. The Beijerinckia treatment resulted in a leaf yield
equal to that from the recommended dose of N and Azospirillum reduced leaf yield in comparison to
that from the recommended N treatment although the yield from Azospirillum treatment was more
than that from the culture medium treatments. A combination of NFBs where Azotobacter was one
of the components improved leaf yield over single NFB treatments. NFBs also resulted in improved
leaf quality as indicated by their protein content and their impact on silkworm rearing and cocoon
production when treated leaves were subjected to bioassay. The use of these NFBs, particularly the
Azotobacter, as a foliar biofertilizer to increase mulberry leaf production has not been investigated
before.
Escape and tolerance to high temperature at flowering in groundnut (Arachis hypogaea L.)
Authors: CRAUFURD P. Q. , WHEELER T. R. , ELLIS R. H. , SUMMERFIELD R. J. , VARA PRASAD P. V.
Published: July 2002

Groundnut is an important crop of the semi-arid tropics where potential yields are frequently reduced
by heat and water stress. Eight groundnut genotypes varying in heat tolerance were grown in
controlled environments and exposed to either high (40/28°C) or near-optimum (30/24°C)
temperature from 32 days after sowing (DAS) to maturity. There was significant variation among
genotypes in mainstem leaf number and total flower number at 30/24 and 40/28°C and rates of
appearance were faster at 40/28°C than at 30/24°C. Days from sowing to first flowering varied
among genotypes from 28 to 41 days and therefore the time plants were exposed to high temperature
relative to first flowering ranged from −4 to 9 days. Fruit number for seven out of eight genotypes
at 40/28°C was linearly and negatively related to the time of first flowering relative to the onset of
high temperature (r2 = 0·93; n = l7; P < 0·001), indicating that ‘escape’ was an important component
of heat tolerance in this experiment. Further analysis showed that fruit number in all genotypes at
40/28 °C was closely associated with the cumulative number of flowers that had opened between first
flowering and 3 days after the onset of the high temperature regime (r2 = 0·95; n = 8; P < 0·001).
Variation in fruit number was therefore due both to the timing of flowering and the initial rate of
flower production. These data also suggest that the most sensitive stage of development to high
temperature in groundnut occurred around 3 days before flowers opened. Therefore, it was the timing
of flowering, rather than heat tolerance or susceptibility, that was the dominant attribute determining
fruit number.
Closing Ranks: Montgomery Jews and Civil Rights, 1954–1960
Authors: WEBB CLIVE
Published: July 2002

The arrest of Rosa Parks on 1 December 1955 provided the spark
which
ignited the long smouldering resentments of black Montgomerians. For
381 days they waged a boycott of the city bus lines, frustrating the
opposition of white authorities and financially crippling the local transit

company. More profoundly it resulted in a Supreme Court decision
outlawing segregation on public transportation. Equally momentous was
the emergence of the man who would serve as the spiritual figurehead of

the civil rights movement: Dr. Martin Luther King, Jr.

In the wake of the Montgomery bus boycott, one national black
newspaper acclaimed King as “Alabama's Modern Moses.”
Since the
darkest days of slavery African-Americans had sought spiritual salvation

by comparing their own condition to that of God's Chosen People, the

Israelites of the Old Testament. Throughout their years of enslavement

they prayed for the Moses who would deliver them from their suffering
unto the Promised Land. During the boycott, the black citizens of
Montgomery had similarly sustained their morale by singing the old slave

spirituals, raising their voices at the nightly mass meetings in rousing

renditions of “Go Down Moses, Way Down in Egypt Land.” “As
sure
as Moses got the children of Israel across the Red Sea,” King exhorted
the
black community, “we can stick together and win.” Others too
drew the
analogy between the historical experience of Jews and the contemporary

predicament of African-Americans. Looking back on the boycott, white
liberal activist Virginia Durr evoked the spectre of Nazi Germany in
describing the strength of racist opposition.
Between Girls: Kaye Gibbons'
Ellen Foster and Friendship as a
Monologic Formulation
Authors: MONTEITH SHARON
Published: July 2002

In the work of contemporary writers who explore the racial and social
geography of growing up in the American South, fleeting encounters
between white and black girls abound but enduring friendships prove to
be more problematic to represent. In Ellen Foster (1987), Ellen and
Starletta's association stretches across the novel whereas, most frequently
in fictions, the points at which black and white women converge and
relate tend to be brief and transient, as in Toni Morrison's Beloved (1987)
where a heavily pregnant and fugitive Sethe is aided by poor white Amy;
or in Thulani Davis's 1959 (1992) where the brief kindness of a white
woman is remembered as a significant, if fleeting gesture. I wish to raise
questions about the ways in which cross-racial childhood relationships are
represented formally and aesthetically. There is often an understandable
but troubling literary–critical impasse whereby black girls are contained
within the first-person narrations of white protagonists which, whilst
explicating the connection between the girls, risk engulfing or subsuming
the black “best friend.” I shall examine the ways in which this may be the
inevitable result of the Bildungsroman form and consider how the
representation of the cross-racial friendship at the heart of Ellen Foster is
modified in direct correspondence to the novel's structuring.
DIVORCE IN ETHIOPIA: THE IMPACT OF EARLY MARRIAGE AND CHILDLESSNESS
Authors: TILSON DANA , LARSEN ULLA
Published: July 2002

Forty-five per cent of first marriages in Ethiopia end in divorce within 30 years, and two-thirds of women who divorce do so within the first 5 years of marriage. This paper looks at two factors that may have an impact on the risk of divorce in Ethiopia: early age of first marriage, and childlessness within the first marriage. Data used were from the 1990 National Family and Fertility Survey conducted by the Government of Ethiopia. A total of 8757 women of reproductive age (15–49) were analysed. Life table analysis was used to determine the median age at first marriage, first birth and the median duration of marriage. Cox models were analysed to determine the differentials of divorce. The results of this analysis showed that both early age at marriage and childlessness have a significant impact on the risk of divorce. An inverse relationship was found between age at marriage and risk of divorce. Having a child within the first marriage also significantly reduced the risk of divorce. In addition, several cultural and socioeconomic variables were significant predictors of divorce.
SEASONAL VARIATION OF BIRTHS IN RURAL WEST BENGAL: MAGNITUDE, DIRECTION AND CORRELATES
Authors: CHATTERJEE UMA , ACHARYA RAJIB
Published: July 2002

This paper examines seasonal variation of births in a rural community of West Bengal, India, by exploring data from the 1992–93 National Family Health Survey. Suitable time series analyses were used to determine the seasonal pattern of births and to estimate peaks. The trigonometric regression technique was used to carry out this objective. The study attempted to link the results of the regression analysis to the atmospheric temperature of the region during 1987–91, the distribution of respondents’ husbands’ occupations and the marriage pattern of the community. It was found that, in the study population, conceptions were numerous in the first quarter of a calendar year and the distribution of conceptions over calendar months was negatively associated with the average monthly temperature. In addition, the marriage pattern of the community and the occupational distribution of the fathers also had a significant effect on the distribution of births over calendar months. It is hoped that the findings will boost the development of needs-based maternal and child health (MCH) and family planning programmes in the community.
MID-ARM CIRCUMFERENCE AT BIRTH AS PREDICTOR OF LOW BIRTH WEIGHT AND NEONATAL MORTALITY
Authors: UDDIN AHMED FARID , KARIM ENAMUL , NURJAHAN BHUIYAN SYEDA
Published: July 2002

In Bangladesh, like other developing countries, most births occur at home or in the community, so logistic problems and taboos prevent the weighing of every newborn child. This study was performed to see whether other simpler measurements could be substituted for weight to identify neonates of low birth weight. A total of 1676 live births at the Chittagong Medical College Hospital constituted the study sample, and this showed a high correlation between mid-arm circumference and birth weight (r=0.792, p<0·000). A mid-arm circumference of <9·0 cm had the best sensitivity and specificity for identifying newborns with a birth weight of less than 2500 g. These neonates were followed up to record neonatal deaths. Neonatal mortality showed an inverse relation with mid-arm circumference. A mid-arm circumference of <9·0 cm and a birth weight of <2500 g were equally useful in predicting neonatal outcome. Mid-arm circumference is a simple, quick and reliable indicator for predicting low birth weight and neonatal outcome, and can be easily measured by medical practitioners and traditional birth attendants (TBAs) in the community of developing countries like Bangladesh.
κ-Casein and β-casein alleles in crossbred and Zebu cattle from India
using polymerase chain reaction and sequence-specific
oligonucleotide probes
Authors: MALIK SURESH , KUMAR SATISH , RANI RAJNI
Published: July 2002

Caseins constitute the main part of milk proteins. The genes for the four major
types of casein (CN), αs1-CN, αs2-CN,
β-CN and κ-CN, reside on < 220 kb of the DNA
on bovine chromosome 6 (Threadgill & Womack, 1990). Two casein genes (Cn), β-Cn
and κ-Cn, have been found to be associated with differences in milk production,
cheese yield, protein content, quality and fat yield (Ng-Kwai-Hang et al. 1984). Lin
et al. (1986) have estimated that the combined contributions of αs1-Cn,
β-Cn, κ-Cn and β-lactoglobulin loci accounted for 8·9% of the total
phenotypic variance in milk, 8·6% of that in proteins and 5% of that in fat yield.
Six alleles of κ-Cn gene have so far been identified: κ-CnA,
κ-CnB, κ-CnC, κ-CnE, κ-CnF
and κ-CnG. The κ-CN protein
is 169 amino acids long with varying regions at codons 136 and 148. The A variant
has threonine (ACC) at codon 136 and aspartic acid (GAT) at codon 148, whereas the
B variant has isoleucine (ATC) and alanine (GCT) at codons 136 and 148 respectively
(Mercier et al. 1973). Milk containing κ-CN B was reported to
yield more cheese than that with κ-CN A because it contains more casein and has lower
fat loss. Several studies have shown that cows with the κ-CnBB genotype
produced milk with a higher protein content than cows with κ-CnAA
(Ng-Kwai-Hang et al. 1984; Ron et al. 1994).
Proteolytic specificity of chymosin on caprine αs1-caseins
A and F
Authors: TRUJILLO ANTONIO J. , MIRANDA GUY , LEBARS DOMINIQUE , DELACROIX-BUCHET AGNES
Published: July 2002

From hydrolysis experiments carried out on αs1-caseins

A and F at pH 5·2
in the presence of 30 g NaCl/l, i.e. the conditions encountered in
many young goats'
cheeses, it was found that minima of 19 and 9 bonds were sensitive to chymosin
in
variants A and F respectively. Variant A was hydrolysed faster than variant
F and
the proteolytic pattern (reversed-phase HPLC and polyacrylamide agarose
gel
electrophoresis) differed between the variants. Hydrolysates from both
variants had
a number of cleavage sites in common (Leu20–Leu21,

Phe23–Ala24 and Phe32–Arg33
in
both variants, Leu101–Lys102 and
Leu64–Lys65, Leu120–His121

and Leu83–His84, Leu142–Ala143

and Leu105–Ala106, Leu149–Phe150

and Leu112–Phe113, Leu156–Asp157

and Leu119–Asp120, Trp164–Tyr165

and Trp127–Tyr128 in variants A and F respectively),

while other bonds were split only in variant A (Leu16–Asn17,

Glu18–Asn19, Phe28–Pro29,

Ile44–Gly45, Tyr80–Ile81,

Gln82–Lys83, Tyr91–Leu92,

Tyr94–Leu95, Leu109–Glu110
and
Phe179–Ser180). Major cleavage sites appeared
to be at
Phe23–Val24, Leu142–Ala143
and
Trp164–Tyr165 for variant A, and
Phe23–Val24 and Leu64–Lys65

for variant F. Cleavage site Phe23–Val24
could be the origin of the first breakdown product from goat
αs1-caseins A and F visible in polyacrylamide agarose
gel electrophoresis.
The Olney Autobiographers: English
Conversion Narrative in the Mid-Eighteenth Century
Authors: HINDMARSH D. B.
Published: July 2002

Consider the central religious crisis in the life
of each of three individuals. First, on 21 March 1748, in
the belly of a ship in the
dead of night, awakened by a raging North Atlantic storm which
threatened to sweep all on board to a watery death, John
Newton cries out to God for mercy. Second, at an insane
asylum on 26 July 1764,
William Cowper emerges from nearly a year of psychological
derangement and repeated attempts at self-destruction, and,
flinging himself
into a window-seat in the parlour, he opens a Bible,
reads, and falls into
a spiritual reverie as a kind of divine light floods into
his soul. And then
third, after months of anxiety over his ineffectual pastoral
ministry, and remorse over the levity with which he entered
holy orders, Thomas Scott
shuts himself up in his study with his Bible, the works of
Richard Hooker and other Anglican divines, and by Christmas
1777 argues himself into evangelical conviction.
Annie Besant's Quest for Truth:
Christianity, Secularism and New
Age Thought
Authors: BEVIR MARK
Published: July 2002

Annie Besant was arguably the most famous, or rather infamous,

woman of her age. For much of the 1870s and 1880s she promoted
the secularist cause with remarkable vigour. She became a vice-
president of the National Secular Society, the members of which thought

almost as highly of her as they did of Charles Bradlaugh, the president.
In
1889, however, she joined the Theosophical Society in a sensational move

that shocked even her closest friends. Eventually she became president
of
the Theosophical Society, the members of which again revered her almost

as much as they did its prophet, Madame Blavatsky. Besant moved from
the materialist atheism of the secularists to the New Age thought of the

theosophists. All of her previous biographers have emphasised the contrast

between these two sets of beliefs. They have been unable to recover any

coherence in her activities within the secularist, Fabian and theosophical

movements. Indeed, they have spoken of her many lives, as though she
wandered aimlessly, if enthusiastically, from cause to cause with no
guiding theme whatsoever. When they do look for a pattern in her life,

they typically turn not to her reasons for doing what she did, but rather

to her hidden needs, such as to follow a dominant man or to exercise her

powers. They turn to her emotional make-up to explain her final flight

from reason, and they then explain her earlier commitments by reference

to the emotions they have uncovered. In contrast, I hope to represent
Besant's life as a reasoned quest for truth in the context of the
Victorian
crisis of faith and the social concerns it helped to raise. Besant, with
her
secularism, Fabianism and theosophy, was very much of her time, for
whilst the early part of Queen Victoria's reign was shaped by a religious

movement to make Britain a truly Christian nation and a political
movement to make Britain a democratic nation, the later part of her reign

took its shape from the need to find both a faith capable of surviving
the
rationalist onslaught and solutions to the social problems an extended

franchise had failed to solve.
The wall shear stress produced by the normal impingement of a jet on a flat surface
Authors: PHARES DENIS J. , SMEDLEY GREGORY T. , FLAGAN RICHARD C.
Published: July 2002

A method for the theoretical determination of the wall shear stress under impinging
jets of various configurations is presented. Axisymmetric and two-dimensional
incompressible jets of a wide range of Reynolds numbers and jet heights are considered.
Theoretical predictions from this approach are compared with available wall
shear stress measurements. These data are critically evaluated based on the method
of measurement and its applicability to the boundary layer under consideration. It
was found that impingement-region wall shear stress measurements using the electrochemical
method in submerged impinging liquid jets provide the greatest accuracy
of any indirect method. A unique wall shear stress measurement technique, based
on observing the removal of monosized spheres from well-characterized surfaces, was
used to confirm the impinging jet analysis presented for gas jets. The technique was
also used to determine an empirical relation describing the rise in wall shear stress
due to compressibility effects in impinging high-velocity jets.
Stability and bifurcations in stratified Taylor–Couette flow
Authors: CATON F. , JANIAUD B. , HOPFINGER E. J.
Published: July 2002

In this article we present new experimental and theoretical results which were obtained
for the flow between two concentric cylinders, with the inner one rotating and in the
presence of an axial, stable density stratification. This system is characterized by two
control parameters: one destabilizing, the rotation rate of the inner cylinder; and the
other stabilizing, the stratification.

Two oscillatory linear stability analyses assuming axisymmetric flow conditions
are presented. First an eigenmode linear stability analysis is performed, using the
small-gap approximation. The solutions obtained give insight into the instability
mechanisms and indicate the existence of a confined internal gravity wave mode at
the onset of instability. In the second stability analysis, only diffusion is neglected,
predicting accurately the instability threshold as well as the critical pulsation for all
the stratifications used in the experiments.

Experiments show that the basic, purely azimuthal flow (circular Couette flow) is
destabilized through a supercritical Hopf bifurcation to an oscillatory flow of confined
internal gravity waves, in excellent agreement with the linear stability analysis. The
secondary bifurcation, which takes the system to a pattern of drifting non-axisymmetric
vortices, is a saddle-node bifurcation. The proposed bifurcation diagram shows a
global bifurcation, and explains the discrepancies between previous experimental and
numerical results. For slightly larger values of the rotation rate, weakly turbulent
spectra are obtained, indicating an early appearance of weak turbulence: stationary
structures and defects coexist. Moreover, in this regime, there is a large distribution
of structure sizes. Visualizations of the next regime exhibit constant-wavelength
structures and fluid exchange between neighbouring cells, similar to wavy vortices. Their
existence is explained by a simple energy argument.

The generalization of the bifurcation diagram to hydrodynamic systems with one
destabilizing and one stabilizing control parameter is discussed. A qualitative argument
is derived to discriminate between oscillatory and stationary onset of instability
in the general case.
Accelerated diffusion in the centre of a vortex
Authors: BAJER KONRAD , BASSOM ANDREW P. , GILBERT ANDREW D.
Published: July 2002

The spiral wind-up and diffusive decay of a passive scalar in circular streamlines is
considered. An accelerated diffusion mechanism operates to destroy scalar fluctuations
on a time scale of order P1/3 times the turn-over time, where P is a Péclet number.
The mechanism relies on differential rotation, that is, a non-zero gradient of angular
velocity. However if the flow is smooth, the gradient of angular velocity necessarily
vanishes at the centre of the streamlines, and the time scale becomes greater. The
behaviour at the centre is analysed and it is found that scalar there is only destroyed
on a time scale of order P1/2. Related results are obtained for magnetic field and
for weak vorticity, a scalar coupled to the stream function of the flow. Some exact
solutions are presented.
Large-eddy simulation of turbulent gas–particle flow in a vertical channel: effect of considering inter-particle collisions
Authors: YAMAMOTO Y. , POTTHOFF M. , TANAKA T. , KAJISHIMA T. , TSUJI Y.
Published: July 2002

The interaction between a turbulent gas flow and particle motion was investigated by
numerical simulations of gas–particle turbulent downward flow in a vertical channel.
In particular the effect of inter-particle collision on the two-phase flow field was
investigated. The gas flow field was obtained by large-eddy simulation (LES). Particles
were treated by a Lagrangian method, with inter-particle collisions calculated by a
deterministic method. The spatial resolution for LES of gas–solid two-phase turbulent
flow was examined and relations between grid resolution and Stokes number are
presented. Profiles of particle mean velocity, particle wall-normal fluctuation velocity
and number density are flattened as a result of inter-particle collisions and these
results are in good agreement with experimental measurements. Calculated turbulence
attenuation by particles agrees well with experimental measurements for small Stokes
numbers, but not for large Stokes number particle. The shape and scale of particle
concentrations calculated considering inter-particle collision are in good agreement
with experimental observations.
The stability and transition of the boundary layer on a rotating sphere
Authors: GARRETT S. J. , PEAKE N.
Published: July 2002

This paper is concerned with convective and absolute instabilities in the boundary-layer
flow over the outer surface of a sphere rotating in an otherwise still fluid. Viscous
and streamline-curvature effects are included and the analysis is conducted between
latitudes of 10° and 80° from the axis of rotation. Both convective and absolute
instabilities are found at each latitude within specific parameter spaces. The results of
the convective instability analysis show that a crossflow instability mode is the most
dangerous below θ = 66°. Above this latitude a streamline-curvature mode is found
to be the most dangerous, which coincides with the appearance of reverse flow in the
radial component of the mean flow. At low latitudes the disturbances are considered
to be stationary, but at higher latitudes they are taken to rotate at 76% of the sphere
surface speed, as observed in experimental studies. Our predictions of the Reynolds
number and vortex angle at the onset of convective instability are consistent with
existing experimental measurements. Results are also presented that suggest that the
occurrence of the slowly rotating vortices is associated with the dominance of the
streamline-curvature mode at θ = 66°. The local Reynolds number at the predicted
onset of absolute instability matches experimental data well for the onset of turbulence
at θ = 30°; beyond this latitude the discrepancy increases but remains relatively small
below θ = 70°. It is suggested that this absolute instability may cause the onset of
transition below θ = 70°. Close to the pole the predictions of each stability analysis
are seen to approach those of existing rotating disk investigations.
A general theory for the dynamics of thin viscous sheets
Authors: RIBE N. M.
Published: July 2002

A model for the deformation of thin viscous sheets of arbitrary shape subject to
arbitrary loading is presented. The starting point is a scaling analysis based on
an analytical solution of the Stokes equations for the flow in a shallow (nearly
planar) sheet with constant thickness T0 and principal curvatures
k1 and k2, loaded
by an harmonic normal stress with wavenumbers q1 and q2 in the directions of
principal curvature. Two distinct types of deformation can occur: an ‘inextensional’ (bending) mode when
[mid ]L3(k1q22
+ k2q21)[mid ] [Lt ] ε, and a ‘membrane’
(stretching) mode when [mid ]L3(k1q22
+ k2q21)[mid ] [Gt ] ε, where
L ≡ (q21 + q22)−1/2
and ε = T0/L [Lt ] 1. The scales
revealed by the shallow-sheet solution together with asympotic expansions in powers
of ε are used to reduce the three-dimensional equations for the flow in the sheet
to a set of equivalent two-dimensional equations, valid in both the inextensional
and membrane limits, for the velocity U of the sheet midsurface. Finally, kinematic
evolution equations for the sheet shape (metric and curvature tensors) and thickness
are derived. Illustrative numerical solutions of the equations are presented for a variety
of buoyancy-driven deformations that exhibit buckling instabilities. A collapsing
hemispherical dome with radius L deforms initially in a compressional membrane
mode, except in bending boundary layers of width ∼ (εL)1/2 near a clamped equatorial
edge, and is unstable to a buckling mode which propagates into the dome from that
edge. Buckling instabilities are suppressed by the extensional flow in a sagging inverted
dome (pendant drop), which consequently evolves entirely in the membrane mode. A
two-dimensional viscous jet falling onto a rigid plate exhibits steady periodic folding,
the frequency of which varies with the jet height and extrusion rate in a way similar
to that observed experimentally.
Frame-indifferent and positive-definite Reynolds

stress–strain relation
Authors: WANG LIQIU
Published: July 2002

Both necessary and sufficient conditions are derived in

a systematic, rigorous way

for a Reynolds stress model to preserve both frame indifference and positive

semi-definiteness of the Reynolds stresses and to satisfy the principle
of

material frame

indifference (PMFI). Also developed are two approximate theories, a linear
theory

and a quadratic theory, to simplify the work of developing models satisfying
such

conditions. The results are also valid for the higher-order correlations
and the SGS

Reynolds stresses. This leads to the results either confirming the previous
intuitive

arguments or offering new insights into turbulence modelling, and is of
significance

in clarifying some controversies in the literature, examining how well

existing models preserve the physics, and developing new models.

An examination of various existing models with respect to the necessary
and

sufficient conditions obtained in the present work shows that no one model
can

simultaneously satisfy the invariance, the realizability and the PMFI.
This offers

answers to some fundamental questions regarding the existing models, such
as the

reason why k−ε and k−l models
fail

to give accurate predictions for the normal Reynolds stresses.
Double-diffusive convection instability in a vertical porous enclosure
Authors: MAMOU M. , VASSEUR P. , BILGEN E.
Published: July 2002

The Galerkin and the finite element methods are used to study the
onset of the
double-diffusive convective regime in a rectangular porous cavity.
The two vertical walls of the
cavity are subject to constant fluxes of heat and solute while the two
horizontal ones
are impermeable and adiabatic. The analysis deals with the particular situation
where
the buoyancy forces induced by the thermal and solutal effects are opposing
each other
and of equal intensity. For this situation, a steady rest state solution
corresponding to
a purely diffusive regime is possible. To demonstrate whether the solution
is stable or
unstable, a linear stability analysis is carried out to describe the oscillatory
and the
stationary instability in terms of the Lewis number, Le,
normalized porosity, ε, and the
enclosure aspect ratio, A. Using the Galerkin finite element method,
it is shown that
there exists a supercritical Rayleigh number,
RsupTC, for the onset
of the supercritical
convection and an overstable Rayleigh number,
RoverTC, at which overstability
may
arise. Furthermore, the overstable regime is shown to exist up to a critical
Rayleigh
number, RoscTC, at which

the transition from the oscillatory to direct mode convection
occurs. By using an analytical method based on the parallel flow approximation,
the
convective heat and mass transfer is studied. It is found that, below the
supercritical
Rayleigh number, RsupTC,
there
exists a subcritical Rayleigh number, RsubTC,

at which a stable convective solution bifurcates from the rest state through
finite-amplitude
convection. In the range of the governing parameters considered in this
study, a
good agreement is observed between the analytical predictions and the finite
element
solution of the full governing equations. In addition, it is found that,
for a given value
of the governing parameters, the converged solution can be permanent or
oscillatory,
depending on the porous-medium porosity value, ε.
The influence of rotational and vibrational energy relaxation on boundary-layer
stability
Authors: BERTOLOTTI FABIO P.
Published: July 2002

We investigate the influence of rotational and vibrational energy
relaxation on the
stability of laminar boundary layers in supersonic flows by numerically
solving the
linearized equations of motion for a flow in thermal non-equilibrium. We
model air
as a mixture of nitrogen, oxygen and carbon dioxide, and derive accurate
models
for the relaxation rates from published experimental data in the field
of physical
chemistry. The influence of rotational relaxation is to dampen high-frequency

instabilities, consistent with the well known damping effect of rotational
relaxation on
acoustical waves. The influence of rotational relaxation can be modelled
with acceptable
accuracy through the use of the bulk-viscosity approximation when the bulk

viscosity is computed with a formula described herein. Vibrational relaxation
affects
the growth of disturbances by changing the characteristics of the laminar
mean flow.
The influence is strongest when the flow field contains a region at, or
near, stagnation
conditions, followed by a rapid expansion, such as inside wind tunnels
and around
bodies with a blunt leading edge, whereby the rapid expansion causes the
internal
energy to freeze in a distribution out of equilibrium. For flows at Mach
4.5 and
stagnation temperature of 1000 K, the total amplification exhibited by
boundary-layer
disturbances over a sharp flat plate in wind-tunnel flows can reach a value
that is fifty
times as high as the value computed under the assumption of thermal equilibrium.

The difference in amplification can be twice as high in the case of a blunt
flat plate
at atmospheric flight conditions.
Double diffusive instability in a tall thin slot
Authors: BALMFORTH NEIL J. , BIELLO JOSEPH A.
Published: July 2002

The linear stability of doubly diffusive convection is considered
for a two-dimensional,
Boussinesq fluid in a tall thin slot. For a variety of boundary conditions
on the slot
walls, instability sets in through zero wavenumber over a wide range of
physical
conditions. Long-wave equations governing the nonlinear development of
the instability
are derived. The form of the long-wave equations sensitively depends on
the thermal
and salt boundary conditions; the possible long-wave theories are catalogued.
Finite-amplitude
solutions and their stability are studied. In some cases the finite-amplitude

solutions are not the only possible attractors and numerical solutions
presenting the
alternatives are given. These reveal temporally complicated dynamics.
The structure and dynamics of vorticity and rate
of strain in incompressible homogeneous turbulence
Authors: NOMURA KEIKO K. , POST GARY K.
Published: July 2002

The structure and dynamics of vorticity ω and
rate of strain S are studied using direct
numerical simulations (DNS) of incompressible homogeneous isotropic turbulence.
In
particular, characteristics of the pressure Hessian Π,
which describe non-local interaction
of ω and S, are presented. Conditional
Lagrangian statistics which distinguish
high-amplitude events in both space and time are used to investigate the
physical
processes associated with their evolution. The dynamics are examined on
the principal
strain basis which distinguishes vortex stretching and induced rotation
of the principal
axes of S. The latter mechanism is associated with misaligned
ω with respect
to S, a condition which predominates in isotropic turbulence and
is dynamically
significant, particularly in rotation-dominated regions of the flow. Locally-induced

rotation of the principal axes acts to orient ω
towards the direction of either the
intermediate or most compressive principal strain. The tendency towards
compressive
straining of ω is manifested at the termini of
the high-amplitude tube-like structures
in the flow. Non-locally-induced rotation, associated with Π,
tends to counteract the
locally-induced rotation. This is due to the strong alignment between ω
and the
eigenvector of Π corresponding to its smallest eigenvalue and
is indicative of the
controlling influence of the proximate structure on the dynamics. High-amplitude

rotation-dominated regions deviate from Burgers vortices due to the misalignment
of
ω. Although high-amplitude strain-dominated regions are
promoted primarily by
local dynamics, the associated spatial structure is less organized and
more discontinuous
than that of rotation-dominated regions.
Nonlinear stability of mixed convection
flow under non-Boussinesq conditions.
Part 2. Mean flow characteristics
Authors: SUSLOV S. A. , PAOLUCCI S.
Published: July 2002

Based on amplitude expansions developed in Part 1 (Suslov & Paolucci 1999), we
examine the mean flow characteristics of non-Boussinesq mixed convection flow of
air in a vertical channel in the vicinity of bifurcation points for a wide range of
temperature differences between the walls, and Grashof and Reynolds numbers. The
constant mass flux and constant pressure gradient formulations are shown to lead
to qualitatively similar, but quantitatively different, results. The physical nature of
the distinct shear and buoyancy disturbances is investigated, and detailed mean flow
and energy analyses are presented. The variation of the total mass of fluid in a flow
domain as disturbances develop is discussed. The average Nusselt number and mass
flux are estimated for supercritical regimes for a wide range of governing parameters.
The effect of non-uniformity of modulated wavepackets on the mechanism of
Benjamin–Feir instability
Authors: van DUIN CORNELIS A.
Published: July 2002

The effect of non-uniformity on the development of a modulated, weakly nonlinear
wavepacket is studied. The non-uniformity, characterized by slowly varying wavenumber
and frequency of the primary wave, may lead to significant modification of the
stability properties compared with the uniform case. As a specific example we consider
a modulated Stokes wave on deep water. In the uniform case such a wave proves
to be definitely unstable (Benjamin & Feir 1967). In the non-uniform case, on the
other hand, the wave may become stable under certain conditions. One of these is an
increase of the local group velocity in the direction of wave propagation. Then the
Benjamin-Feir instability mechanism is quenched on a time scale determined by the
degree of non-uniformity. In addition, a sufficient degree of non-uniformity leads to
stability of the wave to linear perturbations. However, when the local group velocity
decreases in the direction of wave propagation, non-uniformity has a destabilizing
effect. A comparison is made with experiments. It is also shown that the analysis,
based on this specific example, is readily applied to a greater variety of non-uniform,
dispersive waves.
Interscale transfer in two-dimensional compact vortices
Authors: PEDRIZZETTI GIANNI , VASSILICOS J. C.
Published: July 2002

The property of transfer between different scales of motion in evolving two-dimensional
compact vortices is studied here, and a general mathematical framework is developed
to describe the transfer between scales inside compact structures. This new approach
is applied to the case of an axisymmetric advection which represents the leading-order
(large time) approximation for Lundgren's family of two-dimensional vortices. It is
also generalized to passive scalar advection by non-axisymmetric velocity fields. It is
shown that scale interactions generated by an axisymmetric advection are essentially
local and dominated by distant triadic interactions: in the case of an evolving spiral
vortex sheet this result is confirmed even when non-axisymmetric corrections are
included. A physical interpretation of the results is given, which can be summarized
by saying that locality of scale interactions is caused by the uniformity of shear
at a given scale and is therefore increasingly natural at small lengthscales. Local
interactions are shown to arise in axisymmetric advection but to be uncommon in
non-axisymmetric advection.
On the baroclinic instability of axisymmetric
rotating gravity currents with bottom slope
Authors: CHOBOTER PAUL F. , SWATERS GORDON E.
Published: July 2002

The baroclinic stability characteristics of axisymmetric gravity currents in a rotating
system with a sloping bottom are determined. Laboratory studies have shown that
a relatively dense fluid released under an ambient fluid in a rotating system will
quickly respond to Coriolis effects and settle to a state of geostrophic balance. Here
we employ a subinertial two-layer model derived from the shallow-water equations to
study the stability characteristics of such a current after the stage at which geostrophy
is attained. In the model, the dynamics of the lower layer are geostrophic to leading
order, but not quasi-geostrophic, since the height deflections of that layer are not small
with respect to its scale height. The upper-layer dynamics are quasi-geostrophic, with
the Eulerian velocity field principally driven by baroclinic stretching and a background
topographic vorticity gradient.

Necessary conditions for instability, a semicircle-like theorem for unstable modes,
bounds on the growth rate and phase velocity, and a sufficient condition for the
existence of a high-wavenumber cutoff are presented. The linear stability equations
are solved exactly for the case where the gravity current initially corresponds to an
annulus flow with parabolic height profile with two incroppings, i.e. a coupled front.
The dispersion relation for such a current is solved numerically, and the characteristics
of the unstable modes are described. A distinguishing feature of the spatial
structure of the perturbations is that the perturbations to the downslope incropping
are preferentially amplified compared to the upslope incropping. Predictions of the
model are compared with recent laboratory data, and good agreement is seen in
the parameter regime for which the model is valid. Direct numerical simulations of
the full model are employed to investigate the nonlinear regime. In the initial stage, the
numerical simulations agree closely with the linear stability characteristics. As the
instability develops into the finite-amplitude regime, the perturbations to the downslope
incropping continue to preferentially amplify and eventually evolve into downslope
propagating plumes. These finally reach the deepest part of the topography, at which
point no more potential energy can be released.
The Anatomy of a Death: Repression,

Human Rights and the Case of Alexandre Vannucchi Leme in

Authoritarian Brazil
Authors: SERBIN KENNETH P.
Published: July 2002

Employing new archival sources, this article

reappraises the role of

human rights in the opposition to Brazil's repressive

military regime. While most

interpretations pinpoint the protest against the 1975

murder of journalist

Vladimir Herzog as the opposition's great awakening,

this research focuses on a

similar outcry against the 1973 killing of University of

São Paulo student

Alexandre Vannucchi Leme. His death led students and

clergymen to defy riot

troops and gather 3,000 people for a memorial service

that was the first large-scale

anti-regime demonstration of the 1970s and a decisive

step in the Roman Catholic

Church's development as leader of the opposition.
The Royalist Regime in the Viceroyalty of Peru, 1820–1824
Authors: FISHER JOHN R.
Published: July 2002

This article provides an analysis of royalist strategy in the viceroyalty
of Peru during the four years between the arrival of José de San Martín's invasion
force in September 1820 and the battle of Ayacucho of December 1824. It pays
particular attention to royalist policy from July 1821, when viceroy José de la
Serna evacuated Lima, the viceregal capital, leaving the city open to San Martín,
who declared independence there on 28 July. Its focus differs, therefore, from
that of most previous commentators on Peru's transition to independence, who
have tended to neglect royalist policy and activity during these crucial final years
in favour of a concentration upon the activities of San Martín, Antonio José de
Sucre, Simón Bolívar and their Peruvian allies. The article begins with a brief
contextual discussion of the historiography of Peruvian independence and
subsequently analyses the main features of historical developments in the
viceroyalty in the period 1810–20. Following substantive discussion of the period
1820–4, it concludes with observations on the historical legacy in Peru of the
royalists' elevation of the city of Cusco to the status of viceregal capital in 1822–4.