bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of bacterial inoculation of unwilted and wilted
grass silages. 1. Rumen microbial activity,
silage nutrient degradability and digestibility
Authors: YAN T. , PATTERSON D. C. , GORDON F. J. , KILPATRICK D. J.
Published: July 2002

A set of four silages, comprising unwilted and wilted silages,

both with and without bacterial
inoculation, was prepared from perennial ryegrass swards on each of eight
harvesting occasions
during the 1994 growing season. The four silages, within a single
harvest, were offered as the total diet
at the maintenance level of feeding to 16 wether sheep in an 8-period change-over
study with
experimental periods of 3 weeks duration, in order to determine
whole tract digestibility and urinary
excretion of purine derivatives (PD). Silage dry matter (DM) and
nitrogen (N) degradabilities were
also examined in the rumen of four rumen-fistulated steers offered a medium
quality silage and a
concentrate supplement at a ratio of 60[ratio ]40 (silage[ratio ]concentrate)

on a DM basis. The data presented
are the mean results obtained across the eight harvests.

There were no significant effects of inoculation on silage pH and
ammonia-N/total-N across the
unwilted and wilted materials. Inoculation of either the unwilted
or wilted silages had no significant
effect on microbial activity in the rumen of sheep, as indicated
from excretion of urinary PD, or on
silage DM or N degradability assessed with rumen-fistulated steers.
However, inoculation significantly
increased the digestibility of organic matter (1·7%, P<0·01),

N (4·6%, P<0·001), energy (2·3%,
P<0·01), neutral detergent fibre (1·5%, P<0·05)

and acid detergent fibre (2·8%, P<0·001) in the

silage. These increases in digestibility following inoculation, in
general derived equally from both the
unwilted and wilted silages. The results indicate that the increase
in silage nutrient digestibility
following inoculation probably reflects a more extensive digestion
in the abomasum and intestine, rather than in the rumen.

Wilting of grass prior to ensiling resulted in silages with significantly

lower pH (5·4%, P<0·05)
and ammonia-N/total-N (42·7%, P<0·001) across

the untreated and inoculant-treated materials.
Wilting also significantly increased (P<0·05) urinary

PD-N output of sheep by 6·9% and silage DM
degradability by steers by 1·6–2·4% across
the untreated and inoculant-treated silages. However,
there were no significant effects of wilting on silage N degradability
and
silage nutrient digestibility.
Volume, surface area and cellular composition of
chewed particles of plant parts of eight forage species
and estimated degradation of cell wall
Authors: WILMAN D. , REZVANI MOGHADDAM P.
Published: July 2002

In order to understand more about the nature of forage particles

before they enter the rumen and
about the degradation of cell walls in the rumen, particles of
different plant parts produced by sheep
when eating each of eight plant species were described in terms of
volume and exposed surface area
and in terms of numbers of cells and volume and surface area of cell
wall. Estimates were made of
the extent to which the walls would be degraded in the rumen. The eight

species were: Trifolium repens
L., Medicago sativa L., Desmodium intortum (Mill.) Urb.,

Lolium perenne L., Festuca arundinacea
Schreb., Chloris gayana Kunth, Cenchrus ciliaris L. and

Zea mays L. In each case early harvesting
was compared with later harvesting in each of two years. The plants were
grown in a heated
glasshouse.

The plant parts which were chewed to the smallest particle size
during eating, and which produced
particles with the largest proportion of total cell wall area exposed
on the outside of the particle
(6–10%), were the legume leaflets and the grass leaf blades and
sheaths. The proportion of total cell
wall area exposed on the outside of chewed particles derived from stems
was
only 3–4%. The number of thick-walled cells per mm3
of chewed particle was greatest in particles derived from the leaf blades

and stems of C. ciliaris, the leaf blades and leaf sheaths of

L. perenne and the stems of C. gayana. The
average number of thick-walled cells per particle was 860000
in particles derived from the stems of
C. gayana and C. ciliaris and 260000 in particles
derived from L. perenne leaf blades and sheaths. The
volume and surface area of walls of thin-walled cells per mm3

were greatest in particles derived from
legume leaflets. The total surface area of walls of epidermal cells per
mm3
was greatest in particles
derived from leaflets and leaf blades and least in those derived from
stems. The estimated percentage
of wall thickness of thick-walled cells which would be degraded in
the rumen was relatively high in
the case of leaf blades, sheaths and stems of C. ciliaris,
leaf blades of Z. mays, leaf sheaths of L.
perenne and F. arundinacea and stems of C. gayana,

relatively low in the case of petioles of T. repens
and stems of D. intortum and M. sativa and close to
zero in legume leaflets. The estimated percentage
of wall thickness which would be degraded did not seem to be related
to the concentration of lignin in the walls, either in grasses or in legumes.
Population fluctuations in three contrasting white
clover cultivars under cutting, with particular reference
to overwintering properties
Authors: FRANKOW-LINDBERG B. E. , von FIRCKS H. A.
Published: July 2002

Three white clover cultivars of differing geographical origin,

namely AberHerald, Grasslands Huia
and Sandra, were grown in binary mixtures with perennial ryegrass
(cv. Preference) for a period of
3 years at Uppsala (59° 49′ N, 17° 39′ E)
where the length of the main growing season is c. 200 days.
Changes in growing point numbers, stolon length and stolon
weight from autumn until late spring
were followed by four to six destructive harvests each season.
Changes in carbohydrate content
(starch and water-soluble carbohydrates) were also determined
on six or seven occasions during the
same time. Cold hardening and dehardening were followed by
artificial freezing tests on stolons
removed from the plots on seven occasions during the last study
season. The rate of node production
was followed in the last spring. Temperatures in the stolon environment

were recorded during the last two study seasons.

All cultivars suffered a loss of stolon length during the winters,
with Huia being most affected. The
extent of recovery during spring varied between years. Late
spring frosts checked the growth of both
AberHerald and Huia more than that of Sandra. The accumulation
of starch appeared to depend on
autumn temperatures and there was a decline in starch content
during the winter. Sandra maintained
a higher content of water-soluble carbohydrates during the
winter and the spring than the other
cultivars. Sandra also achieved a higher degree of freezing
tolerance and dehardened later than both
AberHerald and Huia. However, temperatures in the stolon
environment always exceeded the degree
of freezing tolerance attained irrespective of cultivar.

It is concluded that the accumulation and utilization of
non-structural carbohydrates are important
in determining the extent to which a white clover cultivar survives
the winter and spring in a harsh
climate. Freezing tolerance per se does not seem to be the most

limiting trait, but in a climate where
frequent spring frosts occur, a late dehardening seems to be valuable.
Growth analysis of dry matter accumulation and N
uptake of forage maize cultivars affected by N supply
Authors: GREEF J. M. , OTT H. , WULFES R. , TAUBE F.
Published: July 2002

The productivity of eight forage maize cultivars (Zea mays L.) in response to N was investigated in
a 3-year field experiment located in Northern Germany. Nitrogen fertilizer applications were zero, 50
and 150 kg N/ha given each year shortly after sowing. Each cultivar was grown on the same plot,
beginning in 1993, following the ploughing up of a 2-year old grass sward, to which slurry had been
added. Plants were sampled regularly for dry matter (DM) production and N uptake. A non-linear
regression equation was used to compare the data. Growth analysis and N uptake characteristics
(maximum crop growth rate, duration of maximum crop growth rate, period until maximum crop
growth rate, maximum N uptake rate, duration of maximum N uptake rate, period until maximum
N uptake rate) which derived from the function were used to compare the cultivars.

The cultivars DM yield and N uptake were highest in 1993 and declined in the next two years partly
due to a decrease in soil N mineralization following the ploughing of the grass sward and partly due
to the drier weather conditions during the summers of 1994 and 1995. Duration of the maximum crop
growth rate was greater during the cool year of 1993. In contrast, maximum crop growth rate was
at its highest in the dry vegetation period of 1995. A significant N×cultivar interaction for growth
analysis characteristics (P<0·05) was found in 1995. Cultivars with a high maximum crop growth
rate (above the average value of the eight cultivars tested) and a short duration of maximum crop
growth rate (below the average) accumulated more DM than those genotypes which showed an
inverse relationship.

Increasing N yield was determined by increased maximum N uptake rather than by a greater
duration of maximum N uptake. A significant N×genotype interaction for N uptake parameters
(P<0·05) was found in 1994 and 1995. With some exceptions, cultivars with a high maximum N
uptake rate (above average) accumulated more N per unit area compared to those genotypes which
had low uptake rates. The exceptions had a longer duration of uptake, which could not, however,
compensate for the lower rate. Maximum N uptake rate occurred earlier and duration of maximum
N uptake rate increased compared to the start and duration of maximum crop growth rate. Especially
in 1995, the amount of N taken up before the day of maximum crop growth rate accounted for 71%
of total N uptake. The N uptake rate and the amount of accumulated N until the day of maximum
crop growth rate were highly correlated with DM yield.

This result indicates the availability of genotypic variability in crop growth and N uptake rate to
assist the improvement of DM yield by selection.
Variation within maize lines and hybrids in the absence
of competition and relation between hybrid potential
yield per plant with line traits
Authors: TOKATLIDIS IOANNIS S.
Published: July 2002

The objective of the study was to determine, in the absence of competition (0·74 plants/m2), the
existing variation within lines of maize (Zea mays L.) for plant and ear traits (yield per plant, number
of tillers, number of ears, plant height, number of nodes, ear length, and kernel row number), as well
as the relationship between hybrid potential yield per plant (i.e. yield per plant in the absence of
competition) with line traits. Two categories of material were tested in honeycomb trials, grown from
1989 to 1995 in the University farm of Thessaloniki, Greece. The first category were selections from
long-term inbreds B73 and Mo17, derived through honeycomb design in the absence of competition,
and their crosses. Inbred selections and their crosses were evaluated in different years. For the second
category two sets of S5 lines, A and B, derived through controlled selfing from the commercial single-
cross hybrid PR 3183, were used in random crosses between S5 plants of lines A and B and resulted
in 40 triplets; each triplet included each of the selfed parent, and their hybrid. Triplets of A and B
S6 lines and A × B S5 × S5 crosses were evaluated in the same experiment. Significant differentiation
among lines and hybrids was found for almost all traits; variation within lines for potential yield per
plant, even in case of B73 and Mo17, seemed to be transmissible to the hybrids. Although correlation
values were small in the case of B73 and Mo17 selections, there was a positive correlation between
hybrids and lines for their potential yield per plant. Selection for high yield within S lines gave
‘prolific’ plants, with line prolificacy being correlated with hybrid potential yield per plant.
The Differential of Appearance: Asian American
Cultural Studies
Authors: SHIMA ALAN
Published: July 2002

Lisa Lowe, Immigrant Acts (Durham: Duke University Press,
1996, $16.95).
Pp. 252. ISBN 0 8223 1864 4.

Paul R. Spickard, Japanese Americans: The Formation and Transformation
of an
Ethnic Group (New York: Twayne Publishers, 1996, $28.95). Pp. 225.

ISBN 0 8057 7841 1.

Gordon Chang, Morning Glory, Evening Shadow: Yamato Ichihashi and
his
Internment Writings, 1942–1945 (Stanford: Stanford University
Press, 1997,
£35.00). Pp. 552. ISBN 0 8047 2733 3.

Appearances can be deceiving, sometimes they are fatal. In 1982, Vincent
Chin,
a Chinese-American, entered a Detroit bar with some friends. Ronald Ebens,
a
foreman at a Chrysler automobile plant, and his stepson Michael Nitz, a
laid-off
Chrysler assembly-line worker, also came into the same bar. It is uncertain
what
exactly prompted Ebens to derisively call Chin a “Jap”
and scoff: “It's because
of you motherfuckers that we're out of work!” What is indisputable,
however,
is the sequence of events which took place after the insult. In the wake
of the
abusive remark, a fist-fight erupted between Ebens and Chin. The brawlers
were
evicted from the bar. Ebens and Nitz went to their car and grabbed a baseball
bat.
Observing that Ebens was in possession of a bat, Chin and his companions
fled
from the bar's parking lot. Unwilling to be thwarted by this escape,
Ebens and
Nitz stalked Chin. After a twenty minute pursuit, Ebens and Nitz cornered
Chin.
Nitz held Chin while Ebens beat him on the head with the baseball bat.
Four days
after this attack, Chin died from his head wounds.

What makes the murder of Vincent Chin particularly hideous is the perverse

element of mistaken identity that led to his death. Ronald Ebens took Chin
for
a “Jap.” At one level of interpretation, this visual blunder
comments on the
blind spots of racist thinking, where categorical forms of reasoning isolate
us
between our prejudices and our self-serving interests. Ebens saw an Asian
face
and automatically made it the target of his frustration. At another level
of
interpretation, Eben's racial slur, although inaccurate in ethnically
identifying
Chin, strangely articulates the conceptual incongruities and cultural displacements

that occur in representations of ethnicity and race. Chin's physical
appearance
made him vulnerable to ethnic mistranslation and an eventual victim of
racist
misrepresentation. In short, there is (much like pronouncing two people
husband
and wife) a performative aspect to Ebens's misrecognition of Chin's
identity. To
put it grimly, Chin's figurative transformation literally concluded
in his execution.
American Exceptionalism Reconsidered: Anglo-Saxon Ethnogenesis in the
“Universal” Nation, 1776–1850
Authors: KAUFMANN ERIC
Published: July 2002

The history of nativism in the United States has received considerable
scholarly attention, yet the few systematic attempts to explain it have
focused predominantly on psychological or economic causes. This article
asserts that such explanations fail to address the crucial cultural dimension
of the nativism issue, which must be analyzed through the prism of
historical sociology. Specifically, this article argues that American nativism
cannot be understood without reference to an “American” national
ethnic group whose myth–symbol complex had developed prior to the
large-scale immigration of the mid-nineteenth century. Without understanding
this social construction, it is difficult to explain subsequent
attempts to defend it. This article, therefore, does not seek to retrace the
history of American nativism. Instead, it focuses on the period prior to
1850, when American nativism was in its infancy. It examines the
development of an Anglo-American ethnicity during 1776–1850 and
attempts to delineate its structure. This “American” complex of myths
and symbols, with its attendant set of life-style images and narratives, is
shown to conform to more generally models recently presented by
theorists of ethnicity and nationalism. Finally, it is argued that American
nativism may have exhibited a very different pattern if an “American”
national ethnicity had not taken root.
Traveling in Old and New
Worlds with John Jea, the
African Preacher, 1773–1816
Authors: SAILLANT JOHN
Published: July 2002

Nineteenth-century exslave narratives allow us to understand the way in
which freedmen, freedwomen, and runaways experienced and enjoyed
liberty. In such narratives, liberty, naturally enough, it seems, is the
opposite of slavery. Once free, one was no longer a slave. Yet we should
view this understanding of slavery and freedom as a problem in itself, as
a rhetorical and time-bound use of the notions of enslavement and liberty.
This article argues that an early exslave narrativist, John Jea, articulated
a dichotomous, unrealistic, yet characteristically American, notion of the
relationship between slavery and freedom: that anyone who is not a slave
is free. Expressed in evangelical Protestantism, liberal individualism, and
laissez-faire economics, this notion was a staple of nineteenth-century
American ideology. It is no longer a convincing notion, since it obscures
not only the variety of the experience of slaves, freemen, and freewomen,
but also the forms of bondage that accompanied slavery and survived it.
As a man of the nineteenth century, Jea seems never to have
comprehended the ways that he remained unfree once he was manumitted.
As a black man and exslave, Jea might have been one of those most
sensitive to the persistence of bondage after slavery, but he was not.
Surely this suggests how convincing, yet how false, was new thought
about slavery and freedom in the early nineteenth century.
AN ECOLOGIC STUDY OF THE RELATIONSHIP BETWEEN MEAN BIRTH WEIGHT, TEMPERATURE AND CALORIE CONSUMPTION LEVEL IN JAPAN
Authors: MATSUDA SHINYA , FURUTA MIZUHO , KAHYO HIROAKI
Published: July 2002

This study reports an ecologic analysis of the relationship between mean birth weight (MBW) and nutritional, medical and social variables, using 1982 data for 47 prefectures in Japan.

Correlation analysis showed that variables that correlated significantly with MBW were mean temperature (r=0·63), total calorie intake (r=0·56), and body mass index of women (r=0·60). It is concluded that the MBW level in a given community represents the long and short term nutritional condition of mothers, and that the level may follow Bergman’s law: ‘In the same species, the body size of an animal increases along with latitude; that is, the lower the temperature, the larger the body size’.
REPLY TO LYNN
Authors: MACKINTOSH N. J.
Published: July 2002

Do males and females differ in general intelligence? Lynn (1994, 1998) and I (Mackintosh, 1996) agree that the answer to this question must depend on the answer to two prior questions: what is the definition of general intelligence, and what tests best measure it? Our disagreement arises partly from different answers to these prior questions, but also from differences in our reading of some not wholly consistent evidence. What answers might one give to these prior questions? They are not independent, for a possible (severely operational) definition of general intelligence is that it is a person's score on one particular IQ test battery. Let us start with that simple possibility.
Milk whey protein concentration and mRNA associated with
β-lactoglobulin phenotype
Authors: PROSSER COLIN G. , TURNER SALLY-ANNE , McLAREN ROBERT D. , LANGLEY BRETT , L'HUILLIER PHIL J. , MOLAN PETER , AULDIST MARTIN J.
Published: July 2002

Two common genetic variants of β-lactoglobulin (β-lg), A and B, exist as co-
dominant alleles in dairy cattle (Aschaffenburg, 1968). Numerous studies have shown
that cows homozygous for β-lg A have more β-lg and less α-lactalbumin (α-la) and
casein in their milk than cows expressing only the B variant of β-lg (Ng-Kwai-Hang
et al. 1987; Graml et al. 1989; Hill, 1993; Hill et al. 1995, 1997). These differences have
a significant impact on the processing characteristics of the milk. For instance, the
moisture-adjusted yield of Cheddar cheese is up to 10% higher using milk from cows
of the β-lg BB phenotype compared with milk from cows expressing only the A
variant (Hill et al. 1997). All these studies, however, describe compositional
differences associated with β-lg phenotype in established lactation only. No
information is available on the first few weeks of lactation, when there are marked
changes in the concentrations of β-lg and α-la (Pérez et al. 1990).
Action of cardosin A from Cynara humilis on ovine and caprine caseinates
Authors: SILVA SOFIA V. , MALCATA F. XAVIER
Published: July 2002

In the Iberian Peninsula, the proteinases present in the flowers of members of the
Cynara genus, C. cardunculus, C. humilis and C. scolymus, have for many years been
successfully used in the manufacture of traditional cheeses from ovine and/or caprine
milk on individual farms (Vieira de Sá & Barbosa, 1972; Trujillo et al. 1994). In
Portugal, C. cardunculus is the species most frequently employed. Although
commercial thistle was tentatively assumed to be pure in taxonomic terms, accurate
analyses have shown that the flowers of C. cardunculus are often mixed with flowers
of C. humilis (Pires et al. 1994). The clotting activity of C. humilis is due to an
aspartic proteinase, currently designated cardosin A and similar to another enzyme
obtained from C. cardunculus. This enzyme is similar in specificity and activity to
chymosin (Pires et al. 1994).

The action of cardosin A from C. cardunculus upon ovine and caprine caseins has
been reported recently (Ramalho-Santos et al. 1996; Simo4es, 1998; Sousa & Malcata,
1998), but as yet there is no information on the proteolytic activity of the proteinase
from C. humilis upon caseins from milks other than bovine. Caseins from small
ruminants' milks are the usual substrates of cardosin during milk coagulation and
cheese ripening, and sodium caseinate represents an intermediate system between
isolated caseins and the cheese matrix that is free from interference by fat. Thus
ovine and caprine caseinates may be useful substrates for investigating the
proteolytic activity of cardosin.

The aim of the present study was to compare the action of pure cardosin A,
obtained from C. humilis, on caprine and ovine caseinates, and to assess the in vitro
contribution of this enzyme to the overall proteolytic action of thistle rennet.
Augustine in Byzantium
Authors: LÖSSL JOSEF
Published: July 2002

As Cornelius Mayer wrote recently, the massive output of literature
on Augustine (c. 50,000 extant titles) cannot hide the fact that
‘much scholarly work remains to be done on the enormous variety
and scope of Augustine's influence’. One area of which this is particularly
true is Augustine's impact on Byzantine theology.

While Augustine's own use of Greek patristic literature and contacts
with the Greek patristic world have been investigated for some time and
in some detail, his influence on Greek authors – especially during the later
Byzantine era – has been sadly neglected. However, recent research on
such authors as Maximos Planudes (c. 1255–1305), Gregory Palamas
(1296–1359) and Prochoros Kydones (c. 1333–c. 1370) has done
something to remedy that situation. This paper seeks to present a
summary of that development and provide a context for further study.
God's Disputed Acre
Authors: DYMOND DAVID
Published: July 2002

‘places consecrated to God [should] be venerated by all, and by no
means profaned or in any way violated by a jarring or unsuitable
activity, whether in working, jesting or playing …; [there should be] no
laughter, shouting, immoderate mirth, indecent and indiscreet dances,
indecent mockeries and harmful plays proper to the market-place or the
stage’: letter of Bishop Edmund Lacy of Exeter, 1451

Old churchyards enshrine vast amounts of personal and social
history, although most of it, sadly, is not recoverable.
Furthermore, they often display a romantic and touching beauty.
When exploring villages and towns in all parts of Britain, many of us have
been moved by the sight of a raised platform of hummocky turf
surrounding an ancient Christian church, walled and gated, crossed by
narrow paths, shaded by mature trees, dotted with leaning headstones
and lichened table-tombs, perhaps with the weathered stump of a
medieval preaching cross. Above all we are impressed by the thought
that most of the local population, over many centuries, lies here, ‘each in
his narrow cell for ever laid’. For example, a rural churchyard of half an
acre at Widford in Hertfordshire is estimated to hold more than 5,000
burials, laid to rest over a period of at least 900 years. Such places have
witnessed many solemn rituals: consecration by a bishop, occasional
claims of sanctuary, sad clusters of mourners around open graves, the
commemorative prayers and bell-ringing of All Saints' and All Souls'
days, parochial processions on Palm Sunday or Corpus Christi, and at all
periods the lonely vigils of the bereaved. Repeatedly opened and re-filled
by generations of gravediggers, churchyards are potent reminders of
human mortality which the living have mostly treated with respect, deep
reflection and some superstition.
A linear stability analysis of tidally generated sand waves
Authors: GERKEMA THEO
Published: July 2002

A linear stability analysis is carried out to examine the initial stage of sand-wave
growth under tidal flows and the occurrence of a preferred length scale. The fact that
these bedforms typically have length scales small compared to the tidal excursion is
exploited by adopting an asymptotic approach to solve the hydrodynamic part of the
problem, i.e. to find the hydrodynamic response to an initially small bed perturbation.
This method is shown to have important advantages over previously used methods,
since it allows an exploration of the complete sand-wave regime (whereas other
methods fail for short sand waves), and in general it is also more accurate. It is found
that the selection of a preferred length scale depends mainly on only two parameters
(the bed-slope coefficient, and the ratio of friction velocity to eddy viscosity), whereas
there appears to be almost no dependence on the water depth.
Direct simulation of the turbulent boundary layer along a compression ramp at M = 3 and Reθ = 1685
Authors: ADAMS NIKOLAUS A.
Published: July 2002

The turbulent boundary layer along a compression ramp with a deflection angle of 18° at a free-stream Mach number of M = 3 and a Reynolds number of Reθ = 1685 with respect to free-stream quantities and mean momentum thickness at inflow is studied
by direct numerical simulation. The conservation equations for mass, momentum,
and energy are solved in generalized coordinates using a 5th-order hybrid compact-
finite-difference-ENO scheme for the spatial discretization of the convective fluxes
and 6th-order central compact finite differences for the diffusive fluxes. For time
advancement a 3rd-order Runge–Kutta scheme is used. The computational domain is
discretized with about 15 × 106 grid points. Turbulent inflow data are provided by a
separate zero-pressure-gradient boundary-layer simulation. For statistical analysis, the flow is sampled 600 times over about 385 characteristic timescales δ0/U∞, defined by the mean boundary-layer thickness at inflow and the free-stream velocity. Diagnostics show that the numerical representation of the flow field is sufficiently well resolved.

Near the corner, a small area of separated flow develops. The shock motion is
limited to less than about 10% of the mean boundary-layer thickness. The shock
oscillates slightly around its mean location with a frequency of similar magnitude
to the bursting frequency of the incoming boundary layer. Turbulent fluctuations
are significantly amplified owing to the shock–boundary-layer interaction. Reynolds-stress maxima are amplified by a factor of about 4. Turbulent normal and shear stresses are amplified differently, resulting in a change of the structure parameter.
Compressibility affects the turbulence structure in the interaction area around the
corner and during the relaxation after reattachment downstream of the corner.
Correlations involving pressure fluctuations are significantly enhanced in these regions. The strong Reynolds analogy which suggests a perfect correlation between velocity and temperature fluctuations is found to be invalid in the interaction area.
Energy paths in edge waves
Authors: CHAPMAN C. J.
Published: July 2002

In this paper the energy streamlines, energy paths, and energy streak lines in a steady
or unsteady inhomogeneous acoustic field next to an unstable oscillating boundary,
such as a vortex sheet or shear layer, are determined. The theory in the paper applies
also to an evanescent wave produced by total internal reflection, and to any other
type of edge wave, e.g. a coastally or topographically trapped wave in geophysical
fluid dynamics. The idea of the paper is that energy velocity, i.e. energy flux divided by
energy density, is defined at every point in space and time, not merely when averaged
over a cycle. Integration of the ordinary differential equation for energy velocity as
a function of position and time gives the energy paths. These paths are calculated
explicitly, and are found to have starting and finishing directions very different
from those of cycle-averaged paths. The paper discusses the physical significance of
averaged and non-averaged energy paths, especially in relation to causality. Many
energy paths have cusps, at which the energy velocity is instantaneously zero. The
domain of influence of an arbitrary point on the boundary of a steady acoustic edge
wave is shown to lie within 45° of a certain direction, in agreement with a known result
on shear-layer instability in compressible flow. The results are consistent with flow
visualization photographs of near-field jet noise. The method of the paper determines
domains of influence and causality in any wave problem with an explicit solution, for
example as represented by a Fourier integral.
Acoustic radiation by ocean surface waves
Authors: ARENDT STEVE , FRITTS DAVID C.
Published: July 2002

We calculate the radiation of acoustic waves into the atmosphere by surface gravity
waves on the ocean surface. We show that because of the phase speed mismatch
between surface gravity waves and acoustic waves, a single surface wave radiates
only evanescent acoustic waves. However, owing to nonlinear terms in the acoustic
source, pairs of ocean surface waves can radiate propagating acoustic waves if the
two surface waves propagate in almost equal and opposite directions. We derive an
analytic expression for the acoustic radiation by a pair of ocean surface waves, and
then extend the result to the case of an arbitrary spectrum of ocean surface waves. We
present some examples for both the two-dimensional and three-dimensional regimes.
Of particular note are the findings that the efficiency of acoustic radiation increases
at higher wavenumbers, and the fact that the directionality of the acoustic radiation
is often independent of the shape of the spectrum.
A numerical study of strained three-dimensional wall-bounded turbulence
Authors: COLEMAN G. N. , KIM J. , SPALART P. R.
Published: July 2002

Channel flow, initially fully developed and two-dimensional, is subjected to mean
strains that emulate the effect of rapid changes of streamwise and spanwise pressure
gradients in three-dimensional boundary layers, ducts, or diffusers. As in previous
studies of homogeneous turbulence, this is done by deforming the domain of a
direct numerical simulation (DNS); here however the domain is periodic in only
two directions and contains parallel walls. The velocity difference between the inner
and outer layers is controlled by accelerating the channel walls in their own plane,
as in earlier studies of three-dimensional channel flows. By simultaneously moving
the walls and straining the domain we duplicate both the inner and outer regions
of the spatially developing case. The results are used to address basic physics and
modelling issues. Flows subject to impulsive mean three-dimensionality with and
without the mean deceleration of an adverse pressure gradient (APG) are considered:
strains imitating swept-wing and pure skewing (sideways turning) three-dimensional
boundary layers are imposed. The APG influences the structure of the turbulence,
measured for example by the ratio of shear stress to kinetic energy, much more than
does the pure skewing. For both deformations, the evolution of the Reynolds stress
is profoundly affected by changes to the velocity–pressure-gradient correlation Πij.
This term – which represents the finite time required for the mean strain to modify
the shape and orientation of the turbulent motions – is primarily responsible for the
difference (lag) in direction between the mean shear and the turbulent shear stresses, a
well-known feature of perturbed three-dimensional boundary layers. Files containing
the DNS database and model-testing software are available from the authors for
distribution, as tools for future closure-model testing.
On an instability to Langmuir circulations and the role of Prandtl and Richardson numbers
Authors: PHILLIPS W. R. C.
Published: July 2002

The instability of a weakly sheared density-stratified two-dimensional wavy flow to
longitudinal vortices is considered. The instability mechanism is Craik–Leibovich type
2, or CL2, and the problem is posited in the context of Langmuir circulations beneath
irrotational wind-driven surface waves. Of interest is the influence to the instability
of Prandtl Pr and Richardson Ri numbers according to linear theory. The basis for
the study is an initial value problem posed by Leibovich & Paolucci (1981) in which
the liquid substrate is of semi-infinite extent and the wind-driven current is permitted
to grow in the presence of neutral waves. In the present work Pr is varied from
zero to infinity, and both stabilizing and destabilizing Ri are considered; so too are
monochromatic and measured wave fields, and laminar and turbulent velocity profiles.
Only the Ri = 0 results recover those of Leibovich & Paolucci. For stabilizing Ri,
it is found in general that diminishing Pr are destabilizing to Langmuir circulations
(LCs), and thus that LCs can be present or absent at the same Langmuir number
La provided Ri ≠ 0. It is further found that two branches of neutral curves occur
for some combinations of Pr and Ri, and that minor changes in either parameter
permit the preferred spacing to switch from one branch to the other. In consequence
the preferred spanwise spacing may change from smaller than the wavelength of the
dominant waves to larger than it. Furthermore, although LCs will not form at inverse
La below a global lower bound given by an energy stability analysis, the actual value
of La at onset is found to depend greatly upon local details of the wave and shear
fields. Interestingly although this global lower bound is independent of Ri and Pr
for Ri [ges ] 0, that is not the case for Ri < 0, where it approaches
zero as Ri → −∞, indicating that the CL2 instability is viable even at low Reynolds numbers.
Camassa–Holm, Korteweg–de Vries and related
models for water waves
Authors: JOHNSON R. S.
Published: July 2002

In this paper we first describe the current method for obtaining the Camassa–Holm
equation in the context of water waves; this requires a detour via the Green–Naghdi
model equations, although the important connection with classical (Korteweg–de
Vries) results is included. The assumptions underlying this derivation are described
and their roles analysed. (The critical assumptions are, (i) the simplified structure
through the depth of the water leading to the Green–Naghdi equations, and, (ii)
the choice of submanifold in the Hamiltonian representation of the Green–Naghdi
equations. The first of these turns out to be unimportant because the Green–Naghdi
equations can be obtained directly from the full equations, if quantities averaged
over the depth are considered. However, starting from the Green–Naghdi equations
precludes, from the outset, any role for the variation of the flow properties with depth;
we shall show that this variation is significant. The second assumption is inconsistent
with the governing equations.)

Returning to the full equations for the water-wave problem, we retain both parameters
(amplitude, ε, and shallowness, δ) and then seek a solution as an asymptotic
expansion valid for, ε → 0, δ → 0, independently. Retaining terms O(ε), O(δ2) and
O(εδ2), the resulting equation for the horizontal velocity component, evaluated at
a specific depth, is a Camassa–Holm equation. Some properties of this equation,
and how these relate to the surface wave, are described; the role of this special
depth is discussed. The validity of the equation is also addressed; it is shown that
the Camassa–Holm equation may not be uniformly valid: on suitably short length
scales (measured by δ) other terms become important (resulting in a higher-order
Korteweg–de Vries equation, for example). Finally, we indicate how our derivation
can be extended to other scenarios; in particular, as an example, we produce a
two-dimensional Camassa–Holm equation for water waves.
On the steady separated flow around an inclined flat plate
Authors: YEUNG W. W. H. , PARKINSON G. V.
Published: July 2002

An inviscid analytic model is proposed for the steady

separated flow around an inclined flat plate. With the plate normal

to the stream, the model reduces to the wake-source model of

Parkinson & Jandali originally developed for flow external to a

symmetrical two-dimensional bluff body and its wake. At any other

inclination, the Kutta condition is satisfied at both leading and

trailing edges of the plate, and, in the limit that the angle of

attack approaches zero, classical airfoil theory is recovered. A

boundary condition is formulated based on some experimental results

of Abernathy, but no additional empirical information is required.

The predicted pressure distributions on the wetted surface for a

wide range of angle attack are found to be in good agreement with

experimental data, especially at smaller angles of attack. An

extension to include a leading-edge separation bubble is explored

and results are satisfactory.
Cessation of screech in underexpanded jets
Authors: RAMAN GANESH
Published: July 2002

In significantly underexpanded jets, screech inherently ceases
to exist.

This paper

studies screech cessation in a supersonic rectangular jet and provides
an explanation

for its occurrence. Experimental data are presented for fully expanded
Mach numbers,

Mj, ranging from 1.1 to 1.9. Screech becomes
unsteady

beyond Mj=1.65 and ceases

to exist beyond Mj=1.75. The reason for this
cessation

has remained a mystery, and

this paper examines three suspects: (i) the theory of a frequency mismatch
between

screech tones and the band of the most-amplified jet instability waves,
(ii)

the notion

that Mach disk formation disrupts the shock-cell structure and weakens
the

screech-producing shocks, and (iii) the idea that acoustic feedback and

receptivity diminish at

high levels of underexpansion. A thorough interrogation of experimental
data shows

that (i) is not the main cause of screech cessation here, (ii) plays an

insignificant role,

and (iii) appears to have been largely responsible for screech cessation.
Cessation

occurs because feedback to the jet lip is diminished due to excessive expansion

of the jet boundary. Further, since the jet lip now reflects and scatters
low

intensity sound, the

end result is poor receptivity at the initial shear layer. This theory
is

substantiated by

the re-activation of screech when the nozzle lip thickness is made larger
than the

expanded jet boundary. Finally, increasing lip thickness is seen to produce
a

systematic shift (to higher Mj) of the onset
of

cessation. The results of this study are of direct

relevance to the sonic fatigue problem in aircraft structures, because

understanding screech helps prevent such damage.
Subgrid-scale modelling for the large-eddy

simulation of high-Reynolds-number boundary layers
Authors: KOSOVIĆ BRANKO
Published: July 2002

It has been recognized that the subgrid-scale (SGS) parameterization

represents

a critical component of a successful large-eddy simulation (LES). Commonly
used

linear SGS models produce erroneous mean velocity profiles in LES of high-Reynolds-number boundary layer flows. Although recently proposed approaches

to solving this

problem have resulted in significant improvements, questions about the
true nature

of the SGS problem in shear-driven high-Reynolds-number flows remain open.

We argue that the SGS models must capture inertial transfer effects including

backscatter of energy as well as its redistribution among the normal SGS
stress

components. These effects are the consequence of nonlinear interactions
and

anisotropy.

In our modelling procedure we adopt a phenomenological approach whereby
the

SGS stresses are related to the resolved velocity gradients. We show that
since the

SGS stress tensor is not frame indifferent a more general nonlinear model
can be

applied to the SGS parameterization. We develop a nonlinear SGS model capable
of

reproducing the effects of SGS anisotropy characteristic for shear-driven
boundary

layers. The results obtained using the nonlinear model for the LES of a
neutral

shear-driven atmospheric boundary layer show a significant improvement
in

prediction of the non-dimensional shear and low-order statistics compared
to

the linear

Smagorinsky-type models. These results also demonstrate a profound effect
of the

SGS model on the flow structures.
Dynamics of inviscid capillary breakup:

collapse and pinchoff of a film bridge
Authors: CHEN Y.-J. , STEEN P. H.
Published: July 2002

An axisymmetric film bridge collapses under its own surface tension,

disconnecting at

a pair of pinchoff points that straddle a satellite bubble. The

free-boundary problem

for the motion of the film surface and adjacent inviscid fluid has a finite-time

blowup (pinchoff). This problem is solved numerically using the vortex
method in a

boundary-integral formulation for the dipole strength distribution on the

surface. Simulation

is in good agreement with available experiments. Simulation of the trajectory
up

to pinchoff is carried out. The self-similar behaviour observed near pinchoff
shows

a ‘conical-wedge’ geometry whereby both principal curvatures

of the surface are

simultaneously singular – lengths scale with time as

t2/3. The similarity equations

are written down and key solution characteristics are reported. Prior to
pinchoff,

the following regimes are found. Near onset of the instability, the surface
evolution

follows a direction dictated by the associated static minimal surface problem.
Later,

the motion of the mid-circumference follows a t2/3

scaling. After this scaling ‘breaks’,

a one-dimensional model is adequate and explains the second scaling regime.
Closer

to pinchoff, strong axial motions and a folding surface render the one-dimensional

approximation invalid. The evolution ultimately recovers a

t2/3 scaling and reveals its self-similar structure.
Turbulence, waves and mixing at shear-free density interfaces.
Part 2. Laboratory experiments
Authors: MCGRATH J. L. , FERNANDO H. J. S. , HUNT J. C. R.
Published: July 2002

A laboratory experimental study was performed to
investigate turbulence, waves and
mixing at a sharp density interface (with a jump in buoyancy
Δb), subjected to
shear-free turbulence induced by oscillating grids with typical velocity
and length
scales of uH and
LH, respectively.
The cases where turbulence is present on one
side (single-sided stirring) or on both sides (double-sided
stirring) of the interface
were considered. Extensive flow visualization studies and quantitative
measurements
were performed on the motion field and mixing characteristics at the interface.
It
was found that, rather than any one mechanism controlling the mixing process,

different mechanisms (namely engulfment, generation of waves and their
breaking,
eddy impingement and Kelvin–Helmholtz billows) play
dominant roles over different ranges of the bulk Richardson number
Ri(Ri
=ΔbLH/u2H).

For the Ri range where
wave generation is significant, certain hypotheses and predictions of the
companion
paper by Fernando & Hunt (1997) were tested in detail, by
flow visualization studies
of the qualitative properties of interfacial motions and quantitative measurements

of the r.m.s. fluctuations of interfacial velocity and displacement,
the local gradient
Richardson number within the stratified layer, the frequency spectra and
the related
fractal properties of the interface. The results are
consistent with the hypothesis that,
at high values of Ri(>35), the density interface
consists of linear internal waves
driven by turbulence at high frequencies and breaking waves with sharp
horizontal
gradients of density at low frequencies.
Transitions to complex flows in the Ekman–Couette layer
Authors: HOFFMANN N. , BUSSE F. H. , CHEN W.-L.
Published: July 2002

Secondary and tertiary states of fluid flow in a layer between
two plates in relative
motion and rotating about a normal axis of rotation are studied numerically
for a
wide range of parameters. Plane Couette flow without rotation and the single
Ekman
layer at a rigid plate above a quiescent fluid half-space are obtained
as limiting cases.
A Galerkin method is used for the investigation of the bifurcation structures
of the
problem. A Chebyshev collocation scheme is used for following the evolution
of
time-dependent states of the flow. Comparisons are made with experimental
observations
as well as with previous studies of particular parameter limits.
Fluid flow in a tube with an elastic membrane insertion
Authors: PEDRIZZETTI GIANNI
Published: July 2002

The unsteady flow of a viscous incompressible fluid in a circular
tube with an elastic
insertion is studied numerically. The deformation of the elastic membrane
is obtained
by the theory of finite elasticity whose equations are solved simultaneously
with the
fluid equations in the axisymmetric approximation. The elastic wall expands
outwards
due to the positive transmural pressure and represents an idealized model
for the
response of pathologies in large arteries.

It is found that if either the fluid discharge or the reference pressure
are imposed
downstream of the insertion, the fluid–wall interaction develops
travelling waves along
the membrane whose period depends on membrane elasticity; these are unstable
in a
perfectly elastic membrane and are stabilized by viscoelasticity. In the
reversed system,
when the fluid discharge is imposed on the opposite side, the stable propagation

phenomenon remains the same because of symmetry arguments. Such arguments
do
not apply to the originally unstable behaviour. In this case, even when
the membrane
is perfectly elastic, propagation is damped and two natural fluctuations
appear in the
form of stationary waves. In all cases the resonance of the fluid–wall
interaction has
been analysed. Comparisons with previously observed phenomena and with
results
of analogous studies are discussed.
Role played by the interfacial shear in the
instability mechanism of a viscous liquid jet
surrounded by a viscous gas in a pipe
Authors: LIN S. P. , CHEN J. N.
Published: July 2002

The role of interfacial shear in the onset of instability
of a cylindrical viscous liquid jet
in a viscous gas surrounded by a coaxial circular pipe is elucidated by
use of an energy
budget associated with the disturbance. It is shown that the shear force
at the
liquid–gas interface retards the Rayleigh-mode instability which
leads to the breakup
of the liquid jet into drops of diameter comparable to the jet diameter,
due to capillary
force. On the other hand the interfacial shear and pressure work in concert
to cause the
Taylor-mode instability which leads the jet to break up into droplets of
diameter much
smaller than the jet diameter. While the interfacial pressure plays a slightly
more
important role than the interfacial shear in amplifying the longer-wave
spectrum in the
Taylor mode, the shear stress plays the main role of generating the disturbances
of
shorter wavelength.