bluuebunny/crossref_metadata_2025 huggingface dataset:
EFFECT OF PLANT DENSITY ON THE YIELD OF SORGHUM–COWPEA AND PEARL MILLET–COWPEA INTERCROPS IN NORTHERN NIGERIA
Authors: CRAUFURD P. Q.
Published: July 2002

Three alternate-row intercrop experiments of sorghum (Sorghum bicolor)–cowpea (Vigna unguiculata) and/or millet (Pennisetum glaucum)–cowpea were grown at plant densities of 20 000 to 80 000 plants ha−1 at two locations in northern Nigeria between 1990 and 1992 to examine relations between yield and plant density. These relations were examined using the reciprocals of yield per plant to determine effects of environment, species and genotype on the theoretical maximum yield and optimum plant density. The intercrops were dominated by cereals, and cowpea biomass (BY) and seed yield (SY) were <10% of cereal BY and SY. Cowpea yields decreased as cereal plant density (D) increased, whereas cereal and total intercrop yields increased asymptotically with increasing D. Biomass yield of all intercrops responded to increasing D in a similar manner and the theoretical maximum intercrop BY was 12 290 kg ha−1 in all experiments. The response of SY to D varied among intercrops and was greatest and least with early and late maturing cereals respectively. The optimum D required to produce 90% maximum intercrop BY and SY varied between 15 600 and 30 000 plants ha−1, and 0 (no response to D) and 120 000 plants ha−1 respectively, and was higher for sorghum than for millet intercrops. The implications of these responses for agronomic management and germplasm improvement of cereal–cowpea intercrops are discussed.
MANURE MANAGEMENT BY SMALLHOLDER FARMERS IN THE KANO CLOSE-SETTLED ZONE, NIGERIA
Authors: Harris F. , Yusuf M. A.
Published: July 2002

Manure is a key input to smallholder farming systems, especially in the semi-arid environment of West Africa where cost and availability limit the use of inorganic fertilizers. This paper considers manure management by farmers in an intensive integrated farming system in the Nigerian savanna. The paper reports farmers' indigenous knowledge concerning manure production, quality and application, chemical analysis of manure nutrient content and application rates of manure. The potential manure supply of the livestock population of the Kano close-settled zone is calculated and compared with application rates. Recommendations are made concerning methods for improving manure quality through changes in management practices.
ON-FARM ASSESSMENT OF TWO LIMING MATERIALS IN CABBAGE AND HOT PEPPER CULTIVATION ON ACID SULPHATE SOIL IN GUYANA
Authors: BRANDJES P. J. , LAUCKNER F. B.
Published: July 2002

In researcher-designed, farmer-managed experiments with cabbage and hot pepper, ground seashells (GSS) were compared with low-grade phosphate lime (LGP) at rates of 0, 2.5, 5, 7.5 or 10 t ha−1. A randomized complete block design, with replicates spread over different farms, was used. Liming with GSS or LGP at 10 t ha−1 increased cabbage yield from 0.5 t ha−1 without liming to 15.0 and 5.3 t ha−1 respectively. Hot pepper yield was increased from 2.1 t ha−1 without liming to 3.2 t ha−1 at the three highest rates of GSS and LGP. Application of GSS increased the pH, reduced exchangeable acidity and increased the extractable Ca content of the soil. Partial budget analyses revealed that cabbage and pepper growers obtained highest returns with GSS at 10 and 5 t ha−1 respectively.
ECONOMIC EVALUATION OF USING MULCH FROM MULTI-PURPOSE TREES IN MAIZE-BASED PRODUCTION SYSTEMS IN SOUTH-WESTERN NIGERIA
Authors: Kormawa P. M. , Kamara A. Y. , Jutzi S. C. , Sanginga N.
Published: July 2002

Cutting and carrying of mulch from established tree plots is an alternative to in situ mulch in agroforestry systems. Through the cut-and-carry method, the undesirable effects of tree-crop competition characterized by in situ mulching can be avoided. An economic evaluation of the cut-and-carry method of providing nutrients for maize production was carried out based on investigations in south-western Nigeria. The results showed that the use of mulch from multi-purpose trees (MPTs) through the cut-and-carry method contributed to higher maize grain yields than those obtained with fertilizer or in the untreated controls. However, because of high labour requirements and scarcity of land in the study area, providing nutrients for crop production by this method is unprofitable both in the short and the long term. This may serve as a constraint for the adoption of this technology by farmers. Alternative options requiring less labour and land requirements should be investigated in the quest to replace shifting cultivation.
An unusual complementation in non-excitable mutants in Paramecium
Authors: MATSUDA ATSUSHI , SAIMI YOSHIRO , TAKAHASHI MIHOKO
Published: July 2002

A non-excitable behavioural mutant, d4-662, was previously characterized as the fourth pawn
locus mutant pwD in Paramecium tetraurelia. We now provide data demonstrating that d4-662 is
in fact controlled by a pwB allele that has the unusual feature of complementing other pwB alleles
in heterozygous F1 progeny. Neither the cytoplasm nor the nucleoplasm of d4-662 cured the
mutational defects of pwB and in the reverse combination of d4-662 and pwB, the result was the
same. On the other hand, pwA, another non-excitable mutant, was cured upon cross-injection with
d4-662 and mutants carrying trichocyst non-discharge marker genes were also cured. This
evidence suggests that d4-662 is a new mutant belonging to pwB, and would be better designated
as pwB662. Extensive crossbreeding analyses, however, showed an unusual genetic relationship
between d4-662 and pwB (pwB95 or pwB96).
When d4-662 was crossed with pwB mutants, many
progeny expressing wild-type phenotype or mixed clones of wild-type and pawn cells were obtained
in the F1. Less than 12·5% expressed the pawn phenotype. The appearance of wild-type progeny
in this F1 strongly suggests that an inter-allelic interaction between pwB662
and other pwB alleles may occur during development of the macronucleus.
Devonian plants from Colombia, with discussion of their
geological and palaeogeographical context
Authors: BERRY CHRISTOPHER M. , MOREL EDUARDO , MOJICA JAIRO , VILLARROEL CARLOS
Published: July 2002

Plant fossils are described from the Cuche Formation, Eastern Cordillera, Colombia in the
area of Floresta. Those identified as Colpodexylon cf. deatsii Banks and cf. Archaeopteris sp. suggest
an earliest Late Devonian (Frasnian) age for the formation. These or similar taxa are also found in
contemporaneous deposits in western Venezuela, and other elements of the Venezuelan flora are
found in a geographically intermediate locality. All three Devonian plant localities in the northwest
of South America are within the Colombian Eastern Cordillera and its northern extension, the
Venezuelan Perijá Range, an area that has been integrated as a part of the so-called ‘Eastern Andean
Terrane’ or ‘Central Andean Province’, supposedly accreted to the autochthonous block of the
Guyana Shield during the early Jurassic or before. Although both invertebrates and plants from this
terrane have strong affinities to North American and European assemblages, and might be interpreted
as implying a Laurussian origin for the Eastern Andean Terrane, the evidence is not yet unequivocal,
with some authors postulating an in situ development of this province.
Characterization and origin of a compositionally zoned
aluminous A-type granite from South India
Authors: RAJESH H. M.
Published: July 2002

The Pan-African Ambalavayal granite intrudes the high-grade metamorphic terrain of
northern Kerala, South India and is spatially associated with the Moyar and Calicut lineaments. The
pluton was aligned nearly parallel to the northeast–southwest and east–west faults in the basement,
consistent with magma ascent along pre-existing deep-crustal lineaments in an extensional tectonic
regime. The pluton is characterized by the presence of iron-rich hydrous mafic minerals, primary magnetite,
fO2 above the Ni–NiO buffer and high initial emplacement temperatures near 1000 °C. Modal
and textural analyses reveal two probable compositional zones within the pluton: outer and inner.
Major element variations support this zoning and point to a peralkaline to metaluminous outer zone
and a metaluminous to slightly peraluminous inner zone. Both zones exhibit major and trace element
characteristics of the A-type granites with the outer zone belonging to the A1 subtype and the inner
zone to the A2 subtype of Eby. The trace element trends observed from outer zone to the inner zone
suggests that crystal fractionation may have been the dominant process in the generation of high levels
of the incompatible elements in the case of inner zone samples. The high initial 87Sr/86Sr ratio (0.7135)
and high Y/Nb ratios (Y/Nb > 1.2) are in the range expected for rocks derived from crustal protoliths.
A petrogenetic model involving partial melting of a charnockitic, mafic to intermediate lower crust
followed by limited fractional crystallization of the magma in a high-level magma chamber is proposed.
The enrichment of HFSE and REE (except Eu) in the inner zone is considered the ultimate
product of crystal–melt and volatile activity during the final stage of crystallization in a highly silicic
(SiO2 > 74%) magma chamber.
Thermal history of thrust sheets in an orogenic wedge:
40Ar/39Ar data from the polymetamorphic Seve Nappe
Complex, northern Swedish Caledonides
Authors: SVENNINGSEN OLAF M.
Published: July 2002

The Seve Nappe Complex in the Scandinavian Caledonides contains the fragmented late
Precambrian continent–ocean transition between Baltica and the Iapetus Ocean. This passive margin
was fragmented and thrust eastwards over the Baltic Shield during Caledonian orogenesis. The
individual thrust sheets in the Seve Nappe Complex went through different P–T–t
evolutions, resulting in dramatic metamorphic contrasts: eclogite-bearing nappes are juxtaposed with nappes
showing no evidence of Caledonian deformation or metamorphism in their interiors. Strain
localization to the marginal parts of the thrust sheets left records of both pre-orogenic (rift) and early
orogenic (subduction and subsequent uplift) processes in the thrust sheets of the Seve Nappe
Complex. Even though it has been transported several hundred kilometres, only the margins of the
eastern part of the Sarektjåkkå Nappe are affected by penetrative Caledonian deformation. This part
of the Sarektjåkkå Nappe is dominated by pristine tholeiitic dykes and cross-bedded sandstones. The
dykes are 608±1 Ma old and make up 70–80% of the nappe. Widely spaced thin shear zones of the
Ruopsok fault system represent the only Caledonian penetrative deformation in the interior of the
nappe. Previously published Ar–Ar dates indicate cooling below the closure temperature of hornblende
at c. 470 Ma, but numerous ages have been recorded. Ar dating of biotite and muscovite from a
cross-laminated metapsammite in the Sarektjåkkå Nappe gave well-defined ages of 428.5±3.6 and
432.4±3.8 Ma, respectively. Muscovite from a shear zone in the Ruopsok Fault System gave
428.2±4.0 Ma, whereas hornblende from the same locality did not yield interpretable data. The
results indicate that these rocks were completely degassed at some unknown time, presumably at the
emplacement of the dyke swarm. No subsequent excess argon contamination can be detected. A likely
candidate for the degassing event is the emplacement of the dykes at 608 Ma. The interior of the
nappe, and thus the entire nappe complex, cooled below ∼ 350 °C at around 430 Ma. Cooling from
more than 500 °C at c. 470 Ma to 350 °C at c. 430 Ma suggests an average cooling rate of [les ] 4 °C/Ma. A
prolonged period of slow cooling (≈exhumation?) following the initial, rapid uplift of the eclogite-bearing
nappes and Early Ordovician construction of the Seve Nappe Complex is suggested.
The Pliocene volcanic rocks of Crommyonia, western Greece and

their implications for the early evolution of the South Aegean

arc
Authors: PE-PIPER GEORGIA , HATZIPANAGIOTOU K.
Published: July 2002

Minor Pliocene dacites from Crommyonia mark the western end

of the South Aegean volcanic arc. They form small lava domes and

flows generally associated with extensional faults. An older group

(3.6–4 Ma) occurs in the west and a younger group

(2.3–2.8 Ma) in the east. Volcanic rocks of similar age are

found at Aegina, Poros and Milos in the western part of the South

Aegean arc, whereas volcanism in the eastern part of the arc is of

Quaternary age. The two groups of rocks at Crommyonia are chemically

distinct. Both groups contain multiple generations of plagioclase.

Both have εNd (−8.0 to −10.6) that is

much more negative than any other rocks in the South Aegean arc and

model ages that are similar to those for many Miocene extensional

granites of the Cyclades. The model ages are interpreted to reflect a

mid-Proterozoic mantle event recognized elsewhere in the Hellenides.

The Crommyonia dacitic magmas represent the first stages of melting

of deep lithosphere as a result of both subduction-related hydrous

fluids and extensional decompression. Plagioclase compositions

suggest important magma evolution in a base-of-crust magma chamber,

where the strong crustal Nd isotope signature was acquired. With

time, asthenospheric sources that upwelled as a result of extension

played an increasingly important role in determining the isotopic

characteristics of the arc volcanism.
New perspectives on the order and style of granite

emplacement in the Galway Batholith, western Ireland
Authors: CROWLEY Q. , FEELY M.
Published: July 2002

The late Caledonian Galway Batholith is cut by two major faults

which divide it into three separate

areas: the western, central and eastern blocks. The upthrown and more

deeply eroded central block is

bounded by these faults, in the west by the north–northeast

trending Shannawona Fault and in the east by the

north–northwest trending Barna Fault. We present new granite

field relations from part of the central block

(Inveran sector) which are fundamental in establishing the order

and style of emplacement for the granites

of the central block and the batholith as a whole. Unequivocal field

evidence from the Inveran sector indicates

upward movement of early central block granites which then became the

solid roof rocks to subsequent

intrusions. In the case of the Knock Granite these earlier intrusions

were block stoped. We use this

field evidence to review the geology of the central block in a 200 km2

area that incorporates the previously

mapped Costelloe and Spiddal areas. Sharp intrusive contacts are a

predominant feature of this sector of the

central block and are in marked contrast to the gradational contacts

recorded elsewhere in the batholith.

Whereas juxtaposition of plutons in the western block occurred as

the granites were partly crystallized, the

central block reveals earlier, deeper level granites that were

consolidated by the time they were intruded by

late-stage higher level granites.
Lower Palaeozoic evolution of the

northeast German Basin/Baltica borderland
Authors: McCANN TOMMY
Published: July 2002

The Vendian–Silurian succession from a series

of boreholes in northeast Germany has been petrographically

and geochemically investigated. Evidence suggests that the more

northerly Vendian and

Cambrian succession was deposited on a craton which became

increasingly unstable in Ordovician times.

Similarly, the Ordovician-age succession deposited in the

Rügen area indicates a strongly active continental

margin tectonic setting for the same period. By Silurian times

the region was once more relatively tectonically

quiescent. Although complete closure of the Tornquist Sea was

not complete until latest Silurian times,

the major changes in tectonic regime in the Eastern

Avalonia/Baltica area recorded from the Ordovician suggest

that a significant degree of closure occurred during this time.
Occurrences of Psigraptus and Chigraptus gen. nov.
in the
Tremadoc of the Yukon Territory, Canada
Authors: JACKSON D. E. , LENZ A. C.
Published: July 2002

The full stratigraphical context of the type materials of Psigraptus
arcticus and P. lenzi from
Rock River are given, as well as a new occurrence of the Psigraptus–Adelograptus
Zone in the Upper
Canyon, Peel River of Canada's Yukon Territory. A new monotypic genus
Chigraptus is created for a
quadriradiate anisograptid graptolite with four unbranched first-order
stipes, a horizontal to slightly
reclined rhabdosome and isolate autothecae. The genus is found only at
the base of the Early
Tremadoc Anisograptus–Staurograptus Zone. Chigraptus
may have given rise to the Late Tremadoc
Psigraptus by a reduction in first-order stipes and by increased
reclination.
FRENCH INTELLIGENCE AND HITLER'S RISE TO POWER
Authors: JACKSON PETER
Published: July 2002

This article examines the French response to the rise to power
of Adolf Hitler and the
Nazi party in Germany in January of 1933. It argues that French
intelligence warned civilian and
military leaders that the priorities of the new regime were rearmament
and the militarization of
German society in preparation for a war of conquest. This
essentially accurate appreciation of the
situation inside Germany had little impact on the course of
French foreign policy. At this juncture
French society was preoccupied with worsening economic crisis
and pacifist sentiment had reached its
inter-war zenith. The national focus was inward and domestic
concerns took priority over the external
threat from Germany. Finally, France was in a position of relative
isolation and could garner no
support for a policy of firmness from its erstwhile allies, Great
Britain and the United States. This
combination of national introspection and diplomatic isolation
deterred a succession of governments
from taking determined steps to meet the Nazi challenge in 1933.
WORKING-CLASS RESPECTABILITY: THE EXAMPLE OF THE WESTERN AREAS OF JOHANNESBURG, 1930–55
Authors: GOODHEW DAVID
Published: July 2002

This was no picturesque semi-fairy story. The drunken gambling merry makers
in Bethlehem, heedless of the awful wonder of that night, might easily have been
figures in a Sophiatown street scene on Christmas eve…Later while Mary, Joseph
and the Holy Child were still in the stable, two Roman soldiers descended upon
them – a take off of African Police, complete with assegais and notebook,
demanding to know their tribe, place of birth, and reason for being in Bethlehem…

This description of a nativity play, complete with a send-up of the South
African police, is one snapshot from the life of the Western Areas of
Johannesburg. Others could include a large demonstration to back the wage
demands of teachers and a home-grown police force. Such idiosyncratic and
divergent portraits of community are the backdrop to this study. This article
contends that, in their commitment to religion, education and law and order,
the people of the Western Areas were deeply attached to respectability. The
Western Areas was a cluster of townships – including the famous Sophiatown
– which formed one of the most significant black centres of population in
South Africa in the 1940s and 1950s. The removal of black people from the
Western Areas between 1955 and 1962 constituted one of the most notorious
acts of apartheid and ensured the district's place at the heart of protest
against white domination. Consequently, to assert that respectability was
essential to a working class district such as the Western Areas is to imply that
it had a much wider significance.
Inactivation kinetics of alkaline phosphatase and lactoperoxidase, and denaturation kinetics of β-lactoglobulin in raw milk under isothermal and dynamic temperature conditions
Authors: CLAEYS WENDIE L. , LUDIKHUYZE LINDA R. , VAN LOEY ANN M. , HENDRICKX MARC E.
Published: July 2002

A detailed kinetic study of alkaline phosphatase, lactoperoxidase and β-lactoglobulin
was carried out in the context of identifying intrinsic time–temperature
indicators for controlling the heat processing of milk. The heat inactivation or
denaturation of alkaline phosphatase, lactoperoxidase and β-lactoglobulin under
isothermal conditions was found to follow first order kinetics. Experimental results
were analysed using both a two step linear regression and a one step non-linear
regression method. Results obtained using the two statistical techniques were
comparable, but the 95% confidence interval for the predicted values was smaller
when the one step non-linear regression method was used, indicating its superiority
for estimating kinetic parameters. Thermal inactivation of alkaline phosphatase and
lactoperoxidase was characterized by z values of
5·3 deg C (D60 °C = 24·6 min) and
4·3 deg C (D71 °C = 38·6 min) respectively.
For the denaturation of β-lactoglobulin we found z values of
7·9 deg C (D75 °C = 49·9 min) in the temperature range 70–80 °C and
24·2 deg C (D85 °C = 3·53 min) in the range 83-95 °C.
Dref and z were evaluated under
dynamic temperature conditions. To estimate the statistical accuracy of the
parameters, 90% joint confidence regions were constructed.
Expression of bovine β-lactoglobulin transgenic mice
Authors: GUTIÉRREZ-ADÁN ALFONSO , MAGA ELIZABETH A. , BEHBOODI ESMAIL , CONRAD-BRINK JANICE S. , MACKINLAY ANTHONY G. , ANDERSON GARY B. , MURRAY JAMES D.
Published: July 2002

The use of transgenic animals to manipulate milk composition has considerable
potential, both for the production of biomedical proteins and for the direct
manipulation of milk composition for the improvement of dairy animals and their
products (for reviews, see Wall et al. 1992; Yom & Bremel, 1993). Promoters from a
number of milk protein genes from a variety of species have been tested for their
ability to direct the expression of foreign proteins to the mammary gland (for review,
see Maga & Murray, 1995).

β-Lactoglobulin (β-lg) is the major whey protein produced in ruminant milk and
is part of the normal milk composition of most mammals except humans and rodents
(Pervaiz & Brew, 1985). It is expressed at high levels in the mammary gland and is
developmentally regulated. Transgenic mice have been produced using the complete
ovine (Simons et al. 1987; Shani et al. 1992)
and caprine (Ibañez et al. 1997) β-lg genes.
In general, high levels of expression were obtained with the ovine β-lg gene, and
expression was also seen in a position-independent manner (Whitelaw et al. 1992).
Lower levels of expression were reported using the caprine β-lg gene. Here we report
the production of transgenic mice using the bovine β-lg gene. We describe high
expression, position-dependent, and copy number-related expression of bovine β-lg
protein in the milk of six lines of transgenic mice.
The Conclusion of Christina of Markyate's Vita
Authors: KOOPMANS RACHEL M.
Published: July 2002

The Vita of Christina of Markyate has been celebrated as ‘perhaps
the twelfth century's most effective and revealing personal history
of a woman’. Indeed, the Vita's account of Christina's early
career is vivid and remarkably detailed: one can read at length of
Christina's saintly childhood, her efforts to escape an unwanted marriage,
her ascetic hardships living with the hermit Roger and her intimate
spiritual friendship with Abbot Geoffrey of St Albans. But while we know
a great deal about Christina's early career, more than for almost any other
contemporary woman, we know almost nothing about her later life. Her
Vita is incomplete, its text known only from a single fire-damaged
fourteenth-century manuscript, BL, MS Cotton Tiberius E i. Christina's
Vita is the very last item in the Tiberius manuscript. On the final folio, as
Christina is reproving Geoffrey for incorrect behaviour, the text breaks off
at the bottom line in the middle of a word: ‘que minus recte videbatur
gerere sapienter increpando, sa…’. As the last datable reference in the
Vita is to 1139, and Abbot Geoffrey died in 1146, the existing text of the
Vita appears to cover events no later than the early 1140s.
The effects of drag on turbulent gravity currents
Authors: HATCHER LYNNE , HOGG ANDREW J. , WOODS ANDREW W.
Published: July 2002

We model the propagation of turbulent gravity currents through an array of obstacles
which exert a drag force on the flow proportional to the square of the flow speed.
A new class of similarity solutions is constructed to describe the flows that develop
from a source of strength q0tγ. An
analytical solution exists for a finite release, γ = 0,
while power series solutions are developed for sources with γ > 0. These are shown to
provide an accurate approximation to the numerically calculated similarity solutions.
The model is successfully tested against a series of new laboratory experiments which
investigate the motion of a turbulent gravity current through a large flume containing
an array of obstacles. The model is extended to account for the effects of a sloping
boundary. Finally, a series of geophysical and environmental applications of the
model are discussed.
Observations of solitary wave dynamics of film flows
Authors: VLACHOGIANNIS M. , BONTOZOGLOU V.
Published: July 2002

Experimental results are reported on non-stationary evolution and interactions of
waves forming on water and water–glycerol solution flowing along an inclined plane.
A nonlinear wave generation process leads to a large number of solitary humps
with a wide variety of sizes. A uorescence imaging method is applied to capture
the evolution of film height in space and time with accuracy of a few microns.
Coalescence – the inelastic interaction of solitary waves resulting in a single hump – is
found to proceed at a timescale correlated to the difference in height between the
interacting waves. The correlation indicates that waves of similar height do not merge.
Transient phenomena accompanying coalescence are reported. The front-running
ripples recede during coalescence, only to reappear when the new hump recovers its
teardrop shape. The tail of the resulting solitary wave develops an elevated substrate
relative to the front, which decays exponentially in time; both observations about
the tail confirm theoretical predictions. In experiments with water, the elevated back
substrate is unstable, yielding to a tail oscillation with wavelength similar to that of
the front-running ripples. This instability plays a key role in two complex interaction
phenomena observed: the nucleation of a new crest between two interacting solitary
humps and the splitting of a large hump (that has grown through multiple coalescence
events) into solitary waves of similar size.
The influence of low-conductivity boundaries on time-dependent convection
Authors: BUSSE F. H. , PETRY M.
Published: July 2002

The in uence of the thermal conductivity of rigid boundaries is analysed for the

case when the onset of convection occurs in the form of a time-dependent mode. A

new form of long-wavelength convection is found which is disjunct from the high-wavenumber thermal Rossby wave in the presence of infinitely conducting boundaries

usually considered.
The temporal evolution of neutral modes in the impulsively started flow through a circular pipe and their connection to the nonlinear stability of Hagen–Poiseuille flow
Authors: WALTON ANDREW G.
Published: July 2002

The linear stability of the impulsively started flow through a pipe of circular cross-section
is studied at high Reynolds number R. A crucial non-dimensional time of
O(R7/9) is identified at which the disturbance acquires internal flow characteristics.
It is shown that even if the disturbance amplitude at this time is as small as
O(R−22/27) the
subsequent evolution of the perturbation is nonlinear, although it can still be followed
analytically using a multiple-scales approach. The amplitude and wave speed of the
nonlinear disturbance are calculated as functions of time and we show that as t → ∞,
the disturbance evolves into the long-wave limit of the neutral mode structure found
by Smith & Bodonyi in the fully developed Hagen–Poiseuille flow, into which our
basic flow ultimately evolves. It is proposed that the critical amplitude found here
forms a stability boundary between the decay of linear disturbances and ‘bypass’
transition, in which the fully developed state is never attained.
Turbulent flow normal to a triangular cylinder
Authors: HEIST D. K. , GOULDIN F. C.
Published: July 2002

Laser Doppler Velocimetry (LDV) measurements are presented
for a nominally two-dimensional constant-density flow over a
surface-mounted triangular cylinder. The thickness of the boundary
layer approaching the triangular cylinder is much less than the
height of the triangle. Momentum and turbulent kinetic energy
balances are presented and comparisons are made with other separated
and reattaching flows. Also, time domain information is presented in
the form of autocorrelations and spectra. From the energy balances,
the importance of the pressure transport term at the high-speed edge
of the shear layer is seen. Observations of the relationships between
the shapes of the spectra and the details of the energy balance are
made. For example, the slope of the velocity spectra varies from the
free-stream value of −5/3 to a value of −1 in the
middle of the recirculation region. Concurrent with this increase in
slope is a decrease in the role of shear production in the turbulent
kinetic energy balance and an increase in the role of advection and
turbulent transport. From the two-component LDV measurements, a very
low-frequency unsteadiness is shown to contribute energy
preferentially to different components of the velocity fluctuations
depending on the location in the flow.
Dynamic simulation of freely draining flexible

polymers in steady linear flows
Authors: DOYLE PATRICK S. , SHAQFEH ERIC S. G. , GAST ALICE P.
Published: July 2002

We present a study of the rheological and optical behaviour of
Kramers

bead–rod

chains in dilute solution using stochastic computer simulations. We consider
two

model linear flows, steady shear and uniaxial extensional flow, in which
we calculate

the non-Newtonian Brownian and viscous stress contribution of the polymers,
their

birefringence and a stress-optic coefficient. We have developed a computer
algorithm

to differentiate the Brownian from the viscous stress contributions which
also

avoids the order (δt)−1/2 noise associated
with

the Brownian forces. The strain or shear rate is made dimensionless with
a

molecular relaxation time determined by simulated

relaxation of the birefringence and stress after a strong flow is applied.

The characteristic long relaxation time obtained from the birefringence
and

stress are equivalent

and shown to scale with N2 where N is the
number

of beads in the chain.

For small shear or extension rates the viscous contribution to the effective

viscosity is constant and scales as N. We obtain an analytic

expression which explains the

scaling and magnitude of this viscous contribution. In uniaxial extensional
flow we

find an increase in the extensional viscosity with the dimensionless flow
strength

up to a plateau value. Moreover, the Brownian stress also reaches a plateau
and we

develop an analytic expression which shows that the Brownian stress in
an aligned

bead–rod chain scales as N3. Using scaling arguments
we

show that the Brownian stress dominates in steady uniaxial extensional
flow until

large Wi, Wi ≈ 0.06N2,

where Wi is the chain Weissenberg number. In shear flow the viscosity

decays as Wi−1/2 and the first normal stress
as

Wi−4/3 at moderate Wi. We demonstrate
that

these scalings can be understood through a quasi-steady balance of shear
forces with

Brownian forces. For small Wi (in shear and uniaxial extensional
flow)

and for long times (in stress relaxation) the stress-optic law is found
to be

valid. We show that the rheology of the bead–rod chain can be qualitatively

described by an equivalent FENE dumbbell for small Wi.
The influence of entropy fluctuations on the

interaction of turbulence with a shock wave
Authors: MAHESH KRISHNAN , LELE SANJIVA K. , MOIN PARVIZ
Published: July 2002

Direct numerical simulation and inviscid linear analysis are used
to

study the interaction of a normal shock wave with an isotropic turbulent
field

of vorticity and entropy fluctuations. The role of the upstream entropy

fluctuations is emphasized. The upstream correlation between the vorticity
and

entropy fluctuations is shown to strongly influence the evolution of the

turbulence across the shock. Negative upstream correlation between

u′ and T′ is seen to enhance the amplification
of the

turbulence kinetic energy, vorticity and thermodynamic fluctuations across
the shock

wave. Positive upstream correlation has a suppressing effect. An explanation
based

on the relative effects of bulk compression and baroclinic torque is proposed,
and a

scaling law is derived for the evolution of vorticity fluctuations across
the shock.

The validity of Morkovin's hypothesis across a shock wave is examined.
Linear

analysis is used to suggest that shock-front oscillation would invalidate
the

relation between urms and

Trms, as expressed by the hypothesis.
Direct numerical simulations of passive scalars

with Pr>1 advected by turbulent flow
Authors: BOGUCKI DAREK , DOMARADZKI J. ANDRZEJ , YEUNG P. K.
Published: July 2002

Direct numerical simulations of passive scalars, with Prandtl numbers

Pr=3, 5, and

7, advected by turbulence at three low Reynolds numbers were performed.
The energy

spectra are self-similar under the Kolmogorov scaling and

exhibit behaviour consistent

with many other investigations: a short inertial range for the

highest Reynolds number

and the universal exponential form of the spectrum for all Reynolds numbers
in the

dissipation range. In all cases the passive scalar spectra

collapse to a single self-similar curve under the Batchelor scaling and

exhibit the k−1 range followed by an

exponential fall-off. We attribute the applicability of the Batchelor scaling
to our

low-Reynolds-number flows to the universality of the energy dissipation
spectra. The

Batchelor range is observed for wavenumbers in general agreement with experimental

observations but smaller than predicted by the classical estimates. The
discrepancy

is caused by the fact that the velocity scales responsible for the generation
of the

Batchelor range are in the vicinity of the wavenumber of the maximum energy

dissipation, which is one order of magnitude less than the Kolmogorov wavenumber

used in the classical theory. Two different functional forms of

passive scalar spectra

proposed by Batchelor and Kraichnan were fitted to the simulation results
and it was

found that the Kraichnan model agrees very well with the data while the
Batchelor

formula displays systematic deviations from the data.

Implications of these differences

for the experimental procedures to measure the energy and passive scalar
dissipation

rates in oceanographic flows are discussed.
Analysis of Monin–Obukhov similarity from

large-eddy simulation
Authors: KHANNA SAMIR , BRASSEUR JAMES G.
Published: July 2002

A detailed analysis of the predictability of observed

Monin–Obukhov (MO) similarity

within the near-ground region of near-neutral to moderately convective
atmospheric

boundary layers (ABL) from large-eddy simulation (LES) fields is reported
in this

work. High-resolution LES predictions of means, variances, budgets of turbulent

kinetic energy and temperature variance, and the velocity and temperature
spectra

from three ABL states

(−zi/L=0.44, 3 and 8) are
analysed

under MO scaling. The resolution in the near-ground region is increased
by using

‘nested meshes.’ For the close-to-neutral case

(−zi/L=0.44) the relative
roles of

grid resolution and subgrid-scale scale (SGS) parameterization on the

predictability of MO-similarity are also studied.

The simulated temperature field is found to satisfy the MO hypothesis and
agree well

with observations. The simulated velocity field, on the other hand, shows
significant

departures. Except for the horizontal variance, MO scales are the appropriate

normalizing scales for the near-ground-layer statistics. However, the LES
suggest

that the boundary layer depth zi has an

‘indirect’ influence on all near-ground-layer

variables except temperature, and the LES-predicted MO-scaled variables
exhibit a

functional dependence on both z/L and

z/zi. The simulated two-dimensional
spectra

of velocity and temperature fluctuations, however, suggest that while large
scales

deviate from MO-similarity, inertial subrange scales are MO-similar. Discrepancies

with field observations raise important questions of the non-dimensional
depth

z/zi

over which MO-similarity holds for a particular variable. Surface-layer
field studies

generally do not document zi.

It is also not clear to what extent these discrepancies are

due to approximations made in LES. Measurements are needed designed specifically

for comparing with LES predictions.
On the stability of large-amplitude vortices in a
continuously stratified fluid on the f-plane
Authors: BENILOV E. S. , BROUTMAN D. , KUZNETSOVA E. P.
Published: July 2002

The stability of continuously stratified vortices
with large displacement of isopycnal
surfaces on the f-plane is examined both
analytically and numerically. Using an
appropriate asymptotic set of equations, we demonstrated that
sufficiently large
vortices (i.e. those with small values of the Rossby number)
are unstable. Remarkably,
the growth rate of the unstable disturbance is a function of
the spatial coordinates. At
the same time, the corresponding boundary-value problem for
normal modes has no
smooth square-integrable solutions, which would normally
be regarded as stability.

We conclude that (potentially) stable vortices can be
found only among ageostrophic
vortices. Since this assumption cannot be verified
analytically due to complexity of the
primitive equations, we verify it numerically for the
particular case of two-layer stratification.
Gravity currents over porous substrates
Authors: THOMAS L. P. , MARINO B. M. , LINDEN P. F.
Published: July 2002

Results of laboratory experiments are presented in which a fixed
volume of homogeneous
fluid is suddenly released into another fluid of slightly lower density,
over
a horizontal thin metallic grid placed a given distance above the solid
bottom of
a rectangular-cross-section channel. Dense liquid develops as a gravity
current over
the grid at the same time as it partially flows downwards. The results
show that
the gravity current loses mass at an exponential rate through the porous
substrate
with a time constant τ; the front velocity and the head of the current
also decrease
exponentially. The loss of mass dominates the flow and, in contrast to
gravity currents
running over solid bottoms, no self-similar inertial regime seems to be
developed. A
simple model is introduced to explain the scaling law of the loss of mass
and the
evolution of the front position. The flow evolution depends on the characteristic
time
of the initial (slumping) phase and the time constant τ, related to
the initial conditions
and the permeability of the porous substrate, respectively. Qualitative
comparisons
with other gravity currents with loss of mass, such as particle-driven
gravity currents,
are provided.
Spouting and planform selection in the
Rayleigh–Taylor instability of miscible viscous fluids
Authors: RIBE N. M.
Published: July 2002

A weakly nonlinear analysis is used to study the initial evolution
of the
Rayleigh–Taylor instability of two superposed miscible layers of
viscous fluid between
impermeable and traction-free planes in a field of gravity. Analytical
solutions are obtained
to second order in the small amplitude of the initial perturbation of the
interface,
which consists of either rolls or squares or hexagons with a horizontal
wavenumber
k. The solutions are valid for arbitrary values of
k, the viscosity ratio (upper/lower)
γ, and the depth ratio r, but are presented assuming that

k=kmax(γ, r),
where kmax is
the most unstable wavenumber predicted by the linear theory. For all planforms,
the
direction of spouting (superexponential growth of interfacial extrema)
is determined
by the balance between the tendency of the spouts to penetrate the less
viscous layer,
and a much stronger tendency to penetrate the thicker layer. When these
tendencies
are opposed (i.e. when γ>1 with r>1),
the spouts change direction at a critical
value of r=rc(γ).
Hexagons with spouts at their centres are the preferred planform
for nearly all values of γ and r, followed closely
by squares; the most slowly growing
planform is hexagons with spouts at corners. Planform selectivity is strongest
when
γ[ges ]10 and r[ges ]γ1/3.
Application of the results to salt domes in Germany and Iran
show that these correspond to points (γ, r) below the
critical curve r=rc(γ),
indicating that the domes developed
from interfacial extrema having subexponential growth rates.
The transition from density-driven to wave-dominated isolated flows
Authors: MANASSEH RICHARD , CHING CHANG-YUN , FERNANDO HARINDRA J. S.
Published: July 2002

An isolated fluid mass travelling horizontally in a stratified
layer is a phenomenon
described alternatively as a detached gravity-current head or a strongly
nonlinear
solitary wave. A key feature of this flow is the transport of mass. Laboratory

experiments examine the transition in time from a regime in which the flow
is density
driven, to one in which it is wave dominated. A simple means of creating
this
transitional regime, an isolated flow that exhibits both density and wave
effects, is
achieved by dropping a thermal into a linearly stratified layer. This transitional
regime
is called an ‘isolated propagating flow’. Parameters
for which the transitional regime
occurs are identified. Particle-tracking studies reveal the vertical flow
structure. There
is an upper zone that is wave dynamical, and a lower zone in which transport
of
mass occurs. The transported mass slowly leaks out, until the phenomenon
resembles
a weakly nonlinear solitary wave. The experiments mimic a thunderstorm
microburst
impacting a temperature inversion, which has aviation safety implications.
In the
ocean, cracks in the ice cap (polar leads) cause similar flows impacting
the thermocline.
Lattice-Boltzmann simulations of particles in

non-zero-Reynolds-number flows
Authors: QI DEWEI
Published: July 2002

A lattice-Boltzmann method has been developed to simulate suspensions of both

spherical and non-spherical particles in finite-Reynolds-number flows. The results for

sedimentation of a single elliptical particle are shown to be in excellent agreement with

the results of Huang, Hu & Joseph (1998) who used a finite-element method. Sedimentation

of two-dimensional circular and rectangular particles in a two-dimensional

channel and three-dimensional spherical particles in a tube with square cross-section

is simulated. Computational results are consistent with experimentally observed phenomena,

such as drafting, kissing and tumbling.
Experimental and numerical analysis of circular pulse jets
Authors: ISHII R. , FUJIMOTO H. , HATTA N. , UMEDA Y.
Published: July 2002

Unsteady circular jets are treated experimentally and numerically. The time evolution
of circular pulse jets is investigated systematically for a wide range of jet strength,
with the focus on the jet evolution, in particular the formation processes of Mach
disks in the middle stage and of shock-cell structures in the later stage. It is shown
that unsteady second shocks are realized for all sonic underexpanded jets and they
either breed conical shocks for lower pressure ratios or truncated cones (Mach disk
and reflected shock) for higher pressure ratios. The vortex ring produced near the
nozzle lip plays an important role in the formation of the shock-cell structure. In
particular, interactions between the vortex ring and the Mach disk connected with a
strong second shock affect remarkably the formation process of the first shock cell.
Different formation processes of the first cell structure are found. It is also made clear
that the Kelvin–Helmholtz instability along slip surfaces originating from the triple
point at the outer edge of the Mach disk is responsible for the generation of large
second vortices which entrain the first vortex. This results in strong mixing between
the primary jet and surrounding gas for higher pressure ratios. Numerical simulations
with a TVD-scheme for the Euler equations are also performed and the numerical
results are compared with the experimental ones to understand and predict the flow
characteristics of the pulse jets.
Aeroacoustic properties of supersonic elliptic jets
Authors: KINZIE KEVIN W. , McLAUGHLIN DENNIS K.
Published: July 2002

The aerodynamic and acoustic properties of supersonic elliptic and circular jets
are experimentally investigated. The jets are perfectly expanded with an exit Mach
number of approximately 1.5 and are operated in the Reynolds number range of
25 000 to 50 000. The reduced Reynolds number facilitates the use of conventional
hot-wire anemometry and a glow discharge excitation technique which preferentially
excites the varicose or flapping modes in the jets. In order to simulate the high-velocity
and low-density effects of heated jets, helium is mixed with the air jets. This allows
the large-scale structures in the jet shear layer to achieve a high enough convective
velocity to radiate noise through the Mach wave emission process.

Experiments in the present work focus on comparisons between the cold and
simulated heated jet conditions and on the beneficial aeroacoustic properties of the
elliptic jet. When helium is added to the jet, the instability wave phase velocity is
found to approach or exceed the ambient sound speed. The radiated noise is also
louder and directed at a higher angle from the jet axis. In addition, near-field hot-wire spectra are found to match the far-field acoustic spectra only for the helium/air
mixture case. These results demonstrate that there are significant differences between
unheated and heated asymmetric jets in the Mach 1.5 speed range, many of which
have been found previously for circular jets. The elliptic jet was also found to radiate
less noise than the round jet at comparable operating conditions.
On the gravitational displacement of
three-dimensional fluid droplets from inclined
solid surfaces
Authors: DIMITRAKOPOULOS P. , HIGDON J. J. L.
Published: July 2002

The yield conditions for the gravitational displacement of three-dimensional fluid
droplets from inclined solid surfaces are studied through a series of numerical computations.
The study considers both sessile and pendant droplets and includes interfacial
forces with constant surface tension. An extensive study is conducted, covering a wide
range of Bond numbers Bd, angles of inclination β
and advancing and receding contact
angles, θA and θR.
This study seeks the optimal shape of the contact line which yields the maximum displacing force (or
BT ≡ Bd sin β)
for which a droplet can adhere to the surface. The yield conditions
BT are presented as functions of
(Bd or β, θA, Δθ) where
Δθ = θA − θR is the
contact angle hysteresis. The solution of the optimization problem provides an upper bound for
the yield condition for droplets on inclined solid surfaces. Additional contraints based on
experimental observations are considered, and their
effect on the yield condition is determined. The numerical solutions are based on the
spectral boundary element method, incorporating a novel implementation of Newton's
method for the determination of equilibrium free surfaces and an optimization algorithm
which is combined with the Newton iteration to solve the nonlinear optimization
problem. The numerical results are compared with asymptotic theories (Dussan V. &
Chow 1983; Dussan V. 1985) and the useful range of these theories is identified. The
normal component of the gravitational force
BN ≡ Bd cos β
was found to have a weak
effect on the displacement of sessile droplets and a strong effect on the displacement of
pendant droplets, with qualitatively different results for sessile and pendant droplets.