bluuebunny/crossref_metadata_2025 huggingface dataset:
Anisotropic enhancement of turbulence in
large-scale, low-intensity turbulent premixed
propane–air flames
Authors: FURUKAWA JUNICHI , NOGUCHI YOSHIKI , HIRANO TOSHISUKE , WILLIAMS FORMAN A.
Published: September 2002

The density change across premixed flames propagating in turbulent flows modifies
the turbulence. The nature of that modification depends on the regime of turbulent
combustion, the burner design, the orientation of the turbulent flame and the position
within the flame. The present study addresses statistically stationary turbulent combustion
in the flame-sheet regime, in which the laminar-flame thickness is less than
the Kolmogorov scale, for flames stabilized on a vertically oriented cylindrical burner
having fully developed upward turbulent pipe flow upstream from the exit. Under
these conditions, rapidly moving wrinkled laminar flamelets form the axisymmetric
turbulent flame brush that is attached to the burner exit. Predictions have been made
of changes in turbulence properties across laminar flamelets in such situations, but
very few measurements have been performed to test the predictions. The present work
measures individual velocity changes and changes in turbulence across flamelets at
different positions in the turbulent flame brush for three different equivalence ratios,
for comparison with theory.

The measurements employ a three-element electrostatic probe (EP) and a two-component
laser-Doppler velocimeter (LDV). The LDV measures axial and radial
components of the local gas velocity, while the EP, whose three sensors are located
in a vertical plane that passes through the burner axis, containing the plane of the
LDV velocity components, measures arrival times of flamelets at three points in that
plane. From the arrival times, the projection of flamelet orientation and velocity on
the plane are obtained. All of the EP and LDV sensors are located within a fixed
volume element of about 1 mm diameter to provide local, time-resolved information.
The technique has the EP advantages of rapid response and good sensitivity and
the EP disadvantages of intrusiveness and complexity of interpretation, but it is well
suited to the type of data sought here.

Theory predicts that the component of velocity tangent to the surface of a locally
planar flamelet remains constant in passing through the flamelet. The data are
consistent with this prediction, within the accuracy of the measurement. The data
also indicate that the component of velocity normal to the flamelet, measured with
respect to the flamelet, tends to increase in passing through the flamelet, as expected.
The flamelets thereby can generate anisotropy in initially isotropic turbulence. They
also produce differences in turbulent spectra conditioned on unburnt or burnt gas.
Local modifications of turbulence by flamelets thus are demonstrated experimentally.
The modifications are quantitatively different at different locations in the turbulent
flame brush but qualitatively similar in that the turbulence is enhanced more strongly
in the radial direction than in the axial direction at all positions in these flames.
Analysis of the radar reflectivity of aircraft
vortex wakes
Authors: SHARIFF KARIM , WRAY ALAN
Published: September 2002

Radar has been proposed as a way of tracking wake vortices to reduce aircraft spacing
and tests have revealed radar echoes from aircraft wakes in clear air. The mechanism
causing refractive index gradients in these tests is thought to be the same as that
for homogeneous and isotropic atmospheric turbulence in the Kolmogorov inertial
range, for which there is a scattering analysis due to Tatarski. In reality, however,
the structure of aircraft wakes has a significant coherent part superimposed with
turbulence, about whose structure very little is known. This work adopts a picture
of a coherent (in fact two-dimensional) wake to perform a scattering analysis and
calculate the reflected power. In particular, two simple mechanisms causing refractive
index gradients are considered: (A) radial pressure (and therefore density) gradient
in a columnar vortex arising from the rotational flow; (B) adiabatic transport of
atmospheric fluid within a descending oval surrounding a vortex pair. In the scattering
analysis, Tatarski's weak scattering approximation is kept but the usual assumptions
of a far field and a uniform incident wave are dropped. Neither assumption is
generally valid for a wake that is coherent across the radar beam. For analytical
insight, an approximate analysis that invokes, in addition to weak scattering, the far-field
and wide cylindrical beam assumptions, is also developed and compared with
the more general analysis. Reflectivities calculated for the oval (mechanism B) are
within 2–13 dB m2 of the measurements (≈−70 dB m2) of MIT Lincoln Laboratory
at Kwajalein atoll. However, the present predictions have a cut-off away from normal
incidence which is not present in the measurements. This implies that the
two-dimensional picture is not entirely complete. Estimates suggest that the thin layer of
vorticity which is baroclinically generated at the boundary of the oval is turbulent
and this may account for reflectivity away from normal incidence. The reflectivity of a
vortex (mechanism A) is comparable to that of the oval (mechanism B) but occurs at
a frequency (about 50 MHz) that is lower than those considered in all the experiments
to date. This result may be useful because: (i) existing atmospheric radars (known as
ST radars) already operate at this frequency and so the present prediction could be
verified; (ii) rain clutter is not a problem at this frequency; (iii) mechanism A is more
robust because it is independent of atmospheric stratification.
The evolution of strained turbulent
plane wakes
Authors: ROGERS MICHAEL M.
Published: September 2002

Direct numerical simulations of ten turbulent time-evolving strained wakes have
been generated using a pseudo-spectral numerical method. In all the simulations, the
strain was applied to the same (previously generated) initial developed self-similar
wake flow field. The cases include flows in which the wake is subjected to various
orientations of the applied mean strain, including both plane and axisymmetric strain
configurations. In addition, for one particular strain geometry, cases with differing
strain rates were considered. Although classical self-similar analysis does yield a self-similar
solution for strained wakes, this solution does not describe the observed flow
evolution. Instead, the wake mean velocity profiles evolve according to a different
‘equilibrium similarity solution’, with the strained wake width being determined by the
straining in the inhomogeneous cross-stream direction. Wakes that are compressed
in this direction eventually exhibit constant widths, whereas wakes in cases with
expansive cross-stream strain ultimately spread at the same rate as the distortion
caused by the applied strain. The shape of the wake mean velocity deficit profile is
nearly universal. Although the effect of the strain on the mean flow is pronounced
and rapid, the response of the turbulence to the strain occurs more slowly. Changes
in the turbulence intensity cannot keep pace with changes in the mean wake velocity
deficit, even for relatively low strain rates.
Magnetorotational instability of dissipative
Couette flow
Authors: GOODMAN JEREMY , JI HANTAO
Published: September 2002

Axisymmetric stability of viscous resistive magnetized Couette flow is re-examined,
with the emphasis on flows that would be hydrodynamically stable according to
Rayleigh's criterion: opposing gradients of angular velocity and specific angular
momentum. In this regime, magnetorotational instabilities (MRI) may occur. Previous
work has focused on the Rayleigh-unstable regime. To prepare for an experimental
study of MRI, which is of intense astrophysical interest, we solve for global linear
modes in a wide gap with realistic dissipation coefficients. Exchange of stability
appears to occur through marginal modes. Velocity eigenfunctions of marginal modes
are nearly singular at conducting boundaries, but magnetic eigenfunctions are smooth
and obey a fourth-order differential equation in the inviscid limit. The viscous marginal
system is of tenth order; an eighth-order approximation previously used for Rayleigh-unstable
modes does not permit MRI. Peak growth rates are insensitive to boundary
conditions. They are predicted with surprising accuracy by WKB methods even for the
largest-scale mode. We conclude that MRI is achievable under plausible experimental
conditions using easy-to-handle liquid metals such as gallium.
Extension of second-order Stokes theory to variable bathymetry
Authors: BELIBASSAKIS K. A. , ATHANASSOULIS G. A.
Published: September 2002

In the present work second-order Stokes theory has been extended to the case of a
generally shaped bottom profile connecting two half-strips of constant (but possibly
different) depths, initiating a method for generalizing the Stokes hierarchy of second-
and higher-order wave theory, without the assumption of spatial periodicity. In
modelling the wave–bottom interaction three partial problems arise: the first order,
the unsteady second order and the steady second order. The three problems are solved
by using appropriate extensions of the consistent coupled-mode theory developed by
the present authors for the linearized problem. Apart from the Stokes small-amplitude
expansibility assumption, no additional asymptotic assumptions have been introduced.
Thus, bottom slope and curvature may be arbitrary, provided that the resulting wave
dynamics is Stokes-compatible. Accordingly, the present theory can be used for the
study of various wave phenomena (propagation, reflection, diffraction) arising from
the interaction of weakly nonlinear waves with a general bottom topography, in
intermediate water depth. An interesting phenomenon, that is also very naturally
resolved, is the net mass flux induced by the depth variation, which is consistently
calculated by means of the steady second-order potential. The present method has
been validated against experimental results and fully nonlinear numerical solutions.
It has been found that it correctly predicts the second-order harmonic generation,
the amplitude nonlinearity, and the amplitude variation due to non-resonant first-and-second
harmonic interaction, up to the point where the energy transfer to the
third and higher harmonics can no longer be neglected. Under the restriction of
weak nonlinearity, the present model can be extended to treat obliquely incident
waves and the resulting second-order refraction patterns, and to study bichromatic
and/or bidirectional wave–wave interactions, with application to the transformation
of second-order random seas in variable bathymetry regions.
Once again on the supersonic flow separation
near a corner
Authors: KOROLEV G. L. , GAJJAR J. S. B. , RUBAN A. I.
Published: September 2002

Laminar boundary-layer separation in the supersonic flow past a corner point on
a rigid body contour, also termed the compression ramp, is considered based on
the viscous–inviscid interaction concept. The ‘triple-deck model’ is used to describe
the interaction process. The governing equations of the interaction may be formally
derived from the Navier–Stokes equations if the ramp angle θ is represented as θ =
θ0Re−1/4, where θ0 is an order-one quantity and Re is the Reynolds number, assumed
large. To solve the interaction problem two numerical methods have been used. The
first method employs a finite-difference approximation of the governing equations
with respect to both the streamwise and wall-normal coordinates. The resulting
algebraic equations are linearized using a Newton–Raphson strategy and then solved
with the Thomas-matrix technique. The second method uses finite differences in
the streamwise direction in combination with Chebychev collocation in the normal
direction and Newton–Raphson linearization.

Our main concern is with the flow behaviour at large values of θ0. The calculations
show that as the ramp angle θ0 increases, additional eddies form near the corner
point inside the separation region. The behaviour of the solution does not give any
indication that there exists a critical value θ*0 of the ramp angle θ0, as suggested
by Smith & Khorrami (1991) who claimed that as θ0 approaches θ*0, a singularity
develops near the reattachment point, preventing the continuation of the solution
beyond θ*0. Instead we find that the numerical solution agrees with Neiland's (1970)
theory of reattachment, which does not involve any restriction upon the ramp angle.
Linear three-dimensional instability of a
magnetically driven rotating flow
Authors: GRANTS I. , GERBETH G.
Published: September 2002

The instability of a rotating-magnetic-field-driven liquid metal flow in a finite cylinder
with respect to infinitesimal azimuthally periodic perturbations is studied numerically.
This instability is observed to set in prior its axisymmetric counterpart with relatively
low frequency at diameter-to-height ratios between 0.5 and 2. The axisymmetric
and three-dimensional instabilities have similar characteristic features. The instability
originates in the cross-section of the horizontal and vertical rotating boundary layers
and excites inertial waves in the inviscid core.
Buoyancy-driven ventilation between
two chambers
Authors: LIN Y. J. P. , LINDEN P. F.
Published: September 2002

A model of single-room displacement ventilation is extended to a space consisting of
two chambers of equal height connected by two openings. Individually, both chambers
have displacement ventilation in this geometrical arrangement, but the space itself is
not connected to the outside. Thus we are considering ventilation of two chambers in
the interior of a building, such as an office connected to an internal atrium. Theoretical
analysis and experimental results are presented in this paper. The experiments use salt
solutions to simulate thermal forcing in buildings and the theoretical analysis is based
on plume theory. The two chambers have a time-dependent interaction resulting from
changing stratification in the two chambers. We concentrate here on a small chamber
with an internal heat source connected to a large unheated chamber, and show that
the time variation is determined by the size of the larger chamber. We discuss the
implications of these results for building ventilation design and control.
PLIF flow visualization and measurements of the Richtmyer–Meshkov instability of an air/SF6 interface
Authors: COLLINS B. D. , JACOBS J. W.
Published: September 2002

Investigations of the Richtmyer–Meshkov instability carried out in shock tubes have
traditionally used membranes to separate the two gases. The use of membranes, in
addition to introducing other experimental difficulties, impedes the use of advanced
visualization techniques such as planar laser-induced fluorescence (PLIF). Jones &
Jacobs (1997) recently developed a new technique by which a perturbed, membrane-free
gas–gas interface can be created in a shock tube. The gases enter the shock
tube from opposite ends and exit through two small slots on opposite sides of
the test section, forming a stagnation point flow at the interface location. A gentle
rocking motion of the shock tube then provides the initial perturbation in the form
of a standing wave. The original investigation using this technique utilized dense
fog seeding for visualization, which allowed large-scale effects to be observed, but
was incapable of resolving smaller-scale features. PLIF visualization is used in the
present study to investigate the instability generated by two incident shock strengths
(Ms = 1.11 and 1.21), yielding very clear digital images of the flow. Early-time
growth rate measurements obtained from these experiments are found to be in excellent
agreement with incompressible linear stability theory (appropriately adjusted for a
diffuse interface). Very good agreement is also found between the late-time amplitude
measurements and the nonlinear models of Zhang & Sohn (1997) and Sadot et al.
(1998). Comparison of images from the Ms = 1.11 and 1.21 sequences reveals a
significant increase in the amount of turbulent mixing in the higher-Mach-number
experiments, suggesting that a mixing transition has occurred.
Buoyant gravity currents along a sloping bottom in a rotating fluid
Authors: LENTZ STEVEN J. , HELFRICH KARL R.
Published: September 2002

The dynamics of buoyant gravity currents in a rotating reference frame is a classical problem relevant to
geophysical applications such as river water entering the ocean. However, existing scaling theories are
limited to currents propagating along a vertical wall, a situation almost never realized in the ocean. A
scaling theory is proposed for the structure (width and depth), nose speed and flow field characteristics of
buoyant gravity currents over a sloping bottom as functions of the gravity current transport Q,
density anomaly g′, Coriolis frequency f, and bottom slope α. The nose
propagation speed is cp ∼ cw/
(1 + cw/cα) and the width of the buoyant gravity
current is Wp ∼ cw/
f(1 + cw/cα), where
cw = (2Qg′ f)1/4 is the nose propagation
speed in the vertical wall limit (steep bottom slope) and
cα = αg/f is the nose propagation speed
in the slope-controlled limit (small bottom slope). The key non-dimensional parameter
is cw/cα, which indicates whether the bottom slope
is steep enough to be considered a vertical wall
(cw/cα → 0) or approaches the
slope-controlled limit (cw/cα → ∞). The
scaling theory compares well against a new set of laboratory experiments which span steep to gentle bottom
slopes (cw/cα = 0.11–13.1). Additionally,
previous laboratory and numerical model results are reanalysed and shown to support the proposed
scaling theory.
Analysis of singular inertial modes in a spherical
shell: the slender toroidal shell model
Authors: RIEUTORD M. , VALDETTARO L. , GEORGEOT B.
Published: September 2002

We derive the asymptotic spectrum (as the Ekman number E → 0) of axisymmetric
inertial modes when the problem is restricted to two dimensions. We show that the
damping rate of such modes scales with the square root of the Ekman number and that
the width of the shear layers of the eigenfunctions scales with E1/4. The eigenfunctions
obey a Schrödinger equation with a quadratic potential; we provide the analytical
expression for eigenvalues (frequency and damping rate). These results validate the
picture that attractors act like a potential well, trapping inertial waves which resist
confinement owing to viscosity. Using three-dimensional numerical solutions, we
show that the results can be applied to equatorially trapped modes in a thin spherical
shell; in fact, these two-dimensional solutions give the first step (the zeroth order) of a
perturbative approach to three-dimensional solutions in a spherical shell. Our method
is applicable in a straightforward way to any other container where bi-dimensionality
dominates.
Area–volume properties of fluid interfaces
in turbulence: scale-local self-similarity
and cumulative scale dependence
Authors: CATRAKIS HARIS J. , AGUIRRE ROBERTO C. , RUIZ-PLANCARTE JESUS
Published: September 2002

Area–volume properties of fluid interfaces are investigated to quantify the scale-local
and cumulative structure. An area–volume density g3(λ) and ratio Ω3(λ) are introduced
to examine the interfacial behaviour as a function of scale λ or across a range
of scales, respectively. These measures are demonstrated on mixed-fluid interfaces
from whole-field ∼10003 three-dimensional space–time concentration measurements
in turbulent jets above the mixing transition, at Re ∼ 20000 and Sc ∼ 2000, recorded
by laser-induced-fluorescence and digital-imaging techniques, with Taylor's hypothesis
applied. The cumulative structure is scale dependent in Ω3(λ), with a dimension D3(λ)
that increases with increasing scale. In contrast, the scale-local structure exhibits
self-similarity in g3(λ) with an exponent αg ≈1.3 for these interfaces. The scale
dependence in the cumulative structure arises from the large scales, while the self-similarity
corresponds to the small-scale area–volume contributions. The small scales
exhibit the largest area–volume density and provide the dominant contributions to the
total area–volume ratio, which corresponds to ∼10 times the area of a purely large-scale
interface for the present flow conditions. The self-similarity in the scale-local
structure at small scales provides the key ingredient to extrapolate the area–volume
behaviour to higher Reynolds numbers.
Low-Prandtl-number convection in a rotating cylindrical annulus
Authors: PLAUT E. , BUSSE F. H.
Published: September 2002

Motivated by recent experimental results obtained in a low-Prandtl-number fluid
(Jaletzky 1999), we study theoretically the rotating cylindrical annulus model with
rigid boundary conditions. A boundary layer theory is presented which allows a
systematic study of the linear properties of the system in the asymptotic regime of
very fast rotation rates. It shows that the Stewartson layers have a (de)stabilizing
influence at (high) low Prandtl numbers. In the weakly nonlinear regime and for low
Prandtl numbers, a strong retrograde mean flow develops at quadratic order. The
Poiseuille part of this mean flow is determined by an equation obtained by averaging
of the Navier–Stokes equation. It thus gives rise to a new global-coupling term in
the envelope equation describing modulated waves, which can be used for other
systems. The influence of this global-coupling term on the sideband instabilities of the
waves is studied. In the strongly nonlinear regime, the waves restabilize against these
instabilities at small rotation rates, but they are destabilized by a short-wavelength
mode at larger rotation rates. We also find an inversion in the dependence of the
amplitude on the Rayleigh number at low Prandtl numbers and intermediate rotation
rates.
The Master and the Maharajas: The Sikh Princes and the East Punjab Massacres of 1947
Authors: Copland Ian
Published: September 2002

Event

During the spring, summer and autumn of 1947 India's richest province, the Punjab, played host to a massive human catastrophe. The trigger for the catastrophe was Britain's parting gift to its Indian subjects of partition. Confronted by a seemingly intractable demand by the All-India Muslim League for a separate Muslim homeland—Pakistan—a campaign which since 1946 had turned increasingly violent, the British government early in 1947 accepted viceroy Lord Mountbatten's advice that partition was necessary to arrest the country's descent into civil war. ‘Mahatma’ Gandhi notably excepted, the leadership of the Congress party came gradually and reluctantly to the same conclusion. Sardar Vallabhbhai Patel, Jawaharlal Nehru's deputy, likened it to the cutting off of a diseased limb. But in accepting the ‘logic’ of the League's ‘two-nation’ theory, the British applied it remorselessly. They insisted that partition would have to follow the lines of religious affiliation, not the boundaries of provinces. In 1947 League president Muhammad Ali Jinnah was forced to accept what he had contemptuously dismissed in 1944 as a ‘moth-eaten’ Pakistan, a Pakistan bereft of something like half of Bengal and the Punjab and most of Assam.
Miracle or Nightmare?
A Critical Review of Dutch Activation Policies
and their Outcomes
Authors: VAN OORSCHOT WIM
Published: September 2002

This article describes trends in Dutch (un)employment from the 1980s
onwards, it reviews activation measures that were taken in the field of
social security and labour market policies, and it critically discusses the
successfulness of these measures. It concludes that it may not be justified
to attribute the ‘Dutch miracle’ – the recent decrease in unemployment
and the explosive growth of employment – directly to the measures taken,
and that activation policies have endangered social rights and citizenship,
especially of those groups which traditionally are most vulnerable. The
‘Dutch miracle’ is further put into the perspective of a small employment
growth in terms of the total of hours worked annually, the large proportion
of part-time employment, and the large degree of hidden unemployment.
If a future recession hits the Netherlands, the miracle will turn
into a nightmare for many due to the significant overall loss of social
protection.
The construction of the risk of falling among and by older people
Authors: BALLINGER CLAIRE , PAYNE SHEILA
Published: September 2002

Risk is frequently invoked in contemporary accounts of ill health, but its construction is often constrained by a rationalist perspective that focuses on physical causes and functional outcomes, and that presents risk as external to the self and predictable. This paper describes an empirical study of the ways in which risk was realised and managed in a day hospital for older people. An ethnographic approach, with participant observation and semi-structured interviews, and discourse analysis were used to explore these issues with the staff and fifteen users. Whilst the service providers were orientated to the management of physical risk, as through the regimes for administering medication and their attention to risk reduction in the physical environment, the service users were more concerned with the risk to their personal and social identities, and they more frequently described its manifestations in inter-personal exchanges, sometimes as infantalisation and stereotyping. The paper develops this understanding of the potential for falls among older people to elucidate a broader interpretation of risk, and reveals that it is commonly constructed as a challenge to a person's self-image and identity. Such constructions help to explain older people's responses to complex health problems and to the services and treatments that attempt to solve them.
A decade of canopy-tree seedling survival and growth in two Bornean rain forests: persistence and recovery from suppression
Authors: Delissio Lisa J. , Primack Richard B. , Hall Pamela , Lee H. S.
Published: September 2002

The population dynamics of 8500 shade-tolerant tree seedlings of 13 tree species were followed for 10 years at rain forests in Lambir Hills National Park and Bako National Park, Malaysian Borneo. Since these dipterocarp forests have lower rates of canopy gap formation than do rain forests elsewhere, tree seedling biology was predicted to differ. Approximately 50% of seedlings present in 1986 were still alive in 1996. Seven out of thirteen had seedling populations composed predominantly of individuals that were at least 10 years old. These seedlings can undergo alternating periods of relatively rapid and slow growth. Many seedlings that grew rapidly in the first census interval survived through a period of suppression in the second census interval, and conversely many seedlings with a history of suppression had exceptionally high growth in the final census interval. Seedlings of South-East Asian forest tree species are long-lived and appear to be adapted to long periods of suppression in the understorey.
An extreme-value approach to detect clumping and an application to tropical forest gap-mosaic dynamics
Authors: Sheil Douglas , Ducey Mark
Published: September 2002

Although forest tree pattern-dynamics has long been a focus for ecological theory, many aspects of basic analysis remain problematic. This paper describes, examines and illustrates an ‘extreme-value’ approach to clump detection. Simulations demonstrate that the approach, though simple, is sensitive and well suited to identifying aggregation, even in small data sets. The test is complementary to the χ2 approach and significantly outperforms it when high-density clusters form a relatively small fraction of the total area. This difference holds true as density declines, though the power of both tests decreases and the χ2 test eventually fails. Though powerful, the extreme-value tests are slightly conservative. The approach is adaptable to other null distributions and applications. An illustration uses tree data from a Ugandan forest plot with records from 1939 to 1992. One plausible explanation for observed stem increases in this plot is an unusually high incidence of large tree-fall events. Evidence for this is sought through spatial localization of various stem populations. Chi-square tests detect non-random density patterns in the populations that comprise ‘all stems > 10 cm diameter recorded in the 1992 survey’, and ‘all recruits in 1976’. In the extreme-value test three populations are found to be clumped, these are ‘pioneers > 10 cm diameter recorded in the 1992 survey’, ‘all recruits in 1992’ and again ‘all recruits in 1976’. These patterns, particularly the pioneer trees and stem recruitment, signal a ‘gap-dynamic process’ of tree regeneration. Despite this, the trends observed in the Ugandan plot appear unlikely to be caused by tree-falls alone. Various technical and ecological aspects of the extreme-value approach and tree spatial analyses are discussed.
Spatio-temporal patterns of palm endocarp use by three Amazonian forest mammals: granivory or ‘grubivory’?
Authors: Silvius Kirsten M.
Published: September 2002

Infestation rates by palm bruchid beetles (Bruchidae: Pachymerini) on Attalea palm seeds are so high that most endocarps remaining near parent trees contain larvae rather than endosperm a few months after the peak fruiting season. Vertebrates feeding on palm endocarp contents may therefore be feeding on animal rather than plant matter, and the timing of use of endocarps may be influenced by the presence of larvae rather than by background fruit availability. On Maracá Island Ecological Reserve, Roraima State, Brazil, white-lipped peccaries (Tayassu pecari), agoutis (Dasyprocta leporina) and squirrels (Sciurus igniventris) all fed on bruchid beetle larvae from Attalea maripa palm endocarps. Squirrels fed on both larvae and endosperm year-round in all habitat types; agoutis fed on both larvae and seeds only at times and at sites where alternate foods were not available; and white-lipped peccaries fed almost exclusively on bruchid larvae in high-palm-density habitats. Differences in timing and location of endocarp use by these species may provide an index of mammal community dynamics in neotropical forests.
Addressing the information needs of older patients
Authors: Harris Matthew , Bayer Antony , Tadd Win
Published: September 2002

The availability of high-quality, evidence-based, clearly communicated, user-focused information is central to the new NHS. Reliable information empowers patients and their families and enables them to become more knowledgeable about their care and condition following consultation and diagnosis or before a therapeutic intervention. It is an integral part of clinical governance and the clinical risk framework.
Disequilibrium and gait disorders in older people
Authors: Baloh Robert W
Published: September 2002

Disequilibrium is typically described as a feeling of dizziness when standing or walking that is not present while sitting or lying down. Since dizziness is such a common symptom in older people, the symptom may be dismissed as a normal aging phenomenon. On the other hand, the patient may be inappropriately given nonspecific treatment for dizziness such as meclizine or diazepam, which may worsen the condition, due to sedation.
A review of the risk of being born too soon
Authors: Rennie Janet M
Published: September 2002

The true measure of success or failure of perinatal care is not merely neonatal survival, but survival with good health and well-being into childhood and beyond. Quantifying this measure is important for all babies, particularly for those born prematurely. The risks are highest for those with a birthweight less than 1 kg (extremely low birthweight) and/or at less than 26 weeks gestation. There is continuing concern about the burden of illness and disability amongst survivors in this vulnerable group. However, we must not forget that all preterm infants are at increased risk of disability later in childhood and that the same is true for babies born at term who are sick enough to require neonatal intensive care.
Available statistics on premature birth
Authors: Fox Grenville F
Published: September 2002

Premature birth is associated with substantial excess childhood mortality and morbidity and therefore represents an important public health problem worldwide. In the United Kingdom and other industrialised countries it is now the commonest cause of infant mortality. This review will outline the most recently available data for the incidence of premature birth at local, regional, national and international level, and compare them to previously published figures. Any variation in these incidences will be considered along with factors likely to account for these differences. Problems with data collection and analysis will also be discussed.
Effect of delayed enucleation on the developmental potential of nuclear-transferred oocytes receiving adult and fetal fibroblast cells
Authors: Yin Xi Jun , Kato Yoko , Tsunoda Yukio
Published: September 2002

To enhance the probability of reprogramming somatic cell nuclei, fibroblast cells from an adult male rabbit and a 12-day-old fetus were fused with oocytes at the second metaphase. The chromosomes of recipient oocytes were then removed by treatment with demecolcine for 1 or 2 h after fusion. Demecolcine treatment of fused oocytes induced membrane protrusions that contained all the maternal chromosomes, thus making it possible to remove the chromosomes. The potential of nuclear-transferred oocytes to develop into blastocysts was high (48% and 59%) and the average cell number of the blastocysts was large (149 and 159) 96 h after in vitro culture. The proportions of nuclear-transferred oocytes enucleated 1 h after fusion and implanted after transfer to pseudopregnant recipients were relatively high (2.8% and 4.9%) compared with our previous reports (1.7%: Yin et al., 2000; 0.6% and 1.0%: Yin et al., 2002a) where donor cells were fused with previously enucleated oocytes. Of 34 adult somatic cell implantation sites, 6 had fetuses on day 12 or 14 of pregnancy, but none of the fetuses had a heart beat or developed to term. None of the nuclear-transferred oocytes whose chromosomes were removed 2 h after demecolcine treatment implanted after transfer to recipients. The possible reasons why the high-quality nuclear-transferred oocytes did not develop to term are discussed.
Quantification of basigin mRNA in mouse oocytes and preimplantation embryos by competitive RT-PCR
Authors: Ding Nai-Zheng , He Cheng-Qiang , Yang Zeng-Ming
Published: September 2002

Basigin is a member of the immunoglobulin superfamily and a key molecule related to mouse blastocyst implantation. Whether preimplantation mouse embryos express basigin mRNA is still unknown. The aim of this study was to use a quantitative competitive polymerase chain reaction to assess quantitatively the levels of basigin mRNA in mouse oocyte and preimplantation embryos. Basigin mRNA was detected in the oocyte and all the stages of preimplantation embryos. The levels of basigin mRNA were 0.0606 ± 0.0282 in the oocyte, 0.0102 ± 0.0036 in the zygote, 0.0007 ± 0.0003 in the 2-cell embryo, 0.0031 ± 0.0017 in the 4-cell embryo, 0.0084 ± 0.0024 in the 8-cell embryo, 0.0537 ± 0.0121 in the morula and 0.0392 ± 0.0161 attomoles in the blastocyst, respectively. The levels of basigin mRNA in the oocyte, morula and blastocyst were significantly higher than those in the zygote and embryos at the 2-cell, 4-cell and 8-cell stages. The high level of basigin expression in the blastocyst may play a role during embryo implantation.
Generic program monitoring by trace analysis
Authors: JAHIER ERWAN , DUCASSÉ MIREILLE
Published: September 2002

Program execution monitoring consists of checking whole executions for given properties,
and collecting global run-time information. Monitoring gives valuable insights and helps
programmers maintain their programs. However, application developers face the following
dilemma: either they use existing monitoring tools which never exactly fit their needs, or
they invest a lot of effort to implement relevant monitoring code. In this paper, we argue
that when an event-oriented tracer exists, the compiler developers can enable the application
developers to easily code their own monitors. We propose a high-level primitive called foldt
which operates on execution traces. One of the key advantages of our approach is that it
allows a clean separation of concerns; the definition of monitors is totally distinct from both
the user source code and the language compiler. We give a number of applications of the use
of foldt to define monitors for Mercury program executions: execution profiles, graphical
abstract views, and two test coverage measurements. Each example is implemented by a few
simple lines of Mercury.
Regional versus multilateral liberalization of services
Authors: STEPHENSON SHERRY M.
Published: September 2002

Many WTO members have been engaging in efforts at the regional level to liberalize services trade even as they are negotiating under the GATS. This duplication of negotiating effort might appear misplaced, unless regional trade agreements can actually produce results going beyond those at the multilateral level and thus serve the interests of their members. This paper explores in what areas regional agreements on services have surpassed the GATS in terms of delivering on three key objectives set out by all service agreements, namely the promotion of transparency, stability, and liberalization for services trade. The paper comments on how countries may evaluate where to best direct their negotiating efforts, according to the type of service activity in question, and suggests that regional agreements can prove to be useful in supporting and pushing forward multilateral services liberalization.
All Small Nuclear RNAs (snRNAs) of the [U4/U6.U5] Tri-snRNP Localize to Nucleoli; Identification of the Nucleolar Localization Element of U6 snRNA
Authors: Gerbi Susan A. , Lange Thilo Sascha
Published: September 2002

Previously, we showed that spliceosomal U6 small nuclear RNA (snRNA) transiently passes through the nucleolus. Herein, we report that all individual snRNAs of the [U4/U6.U5] tri-snRNP localize to nucleoli, demonstrated by fluorescence microscopy of nucleolar preparations after injection of fluorescein-labeled snRNA into Xenopus oocyte nuclei. Nucleolar localization of U6 is independent from [U4/U6] snRNP formation since sites of direct interaction of U6 snRNA with U4 snRNA are not nucleolar localization elements. Among all regions in U6, the only one required for nucleolar localization is its 3′ end, which associates with the La protein and subsequently during maturation of U6 is bound by Lsm proteins. This 3′-nucleolar localization element of U6 is both essential and sufficient for nucleolar localization and also required for localization to Cajal bodies. Conversion of the 3′ hydroxyl of U6 snRNA to a 3′ phosphate prevents association with the La protein but does not affect U6 localization to nucleoli or Cajal bodies.
α4β1 Integrin Regulates Lamellipodia Protrusion via a Focal Complex/Focal Adhesion-independent Mechanism
Authors: Pinco Karen A. , He Wei , Yang Joy T.
Published: September 2002

α4β1 integrin plays an important role in cell migration. We show that when ectopically expressed in Chinese hamster ovary cells, α4β1 is sufficient and required for promoting protrusion of broad lamellipodia in response to scratch-wounding, whereas α5β1 does not have this effect. By time-lapse microscopy of cells expressing an α4/green fluorescent protein fusion protein, we show that α4β1 forms transient puncta at the leading edge of cells that begin to protrude lamellipodia in response to scratch-wounding. The cells expressing a mutant α4/green fluorescent protein that binds paxillin at a reduced level had a faster response to scratch-wounding, forming α4-positive puncta and protruding lamellipodia much earlier. While enhancing lamellipodia protrusion, this mutation reduces random motility of the cells in Transwell assays, indicating that lamellipodia protrusion and random motility are distinct types of motile activities that are differentially regulated by interactions between α4β1 and paxillin. Finally, we show that, at the leading edge, α4-positive puncta and paxillin-positive focal complexes/adhesions do not colocalize, but α4β1 and paxillin colocalize partially in ruffles. These findings provide evidence for a specific role of α4β1 in lamellipodia protrusion that is distinct from the motility-promoting functions of α5β1 and other integrins that mediate cell adhesion and signaling events through focal complexes and focal adhesions.
Membrane Trafficking of Heterotrimeric G Proteins via the Endoplasmic Reticulum and Golgi
Authors: Michaelson David , Ahearn Ian , Bergo Martin , Young Stephen , Philips Mark
Published: September 2002

Membrane targeting of G-protein αβγ heterotrimers was investigated in live cells by use of Gα and Gγ subunits tagged with spectral mutants of green fluorescent protein. Unlike Ras proteins, Gβγ contains a single targeting signal, the CAAX motif, which directed the dimer to the endoplasmic reticulum. Endomembrane localization of farnesylated Gγ1, but not geranylgeranylated Gγ2, required carboxyl methylation. Targeting of the heterotrimer to the plasma membrane (PM) required coexpression of all three subunits, combining the CAAX motif of Gγ with the fatty acyl modifications of Gα. Gα associated with Gβγ on the Golgi and palmitoylation of Gα was required for translocation of the heterotrimer to the PM. Thus, two separate signals, analogous to the dual-signal targeting mechanism of Ras proteins, cooperate to target heterotrimeric G proteins to the PM via the endomembrane.
A Rab8-specific GDP/GTP Exchange Factor Is Involved in Actin Remodeling and Polarized Membrane Transport
Authors: Hattula Katarina , Furuhjelm Johanna , Arffman Airi , Peränen Johan
Published: September 2002

The mechanisms mediating polarized delivery of vesicles to cell surface domains are poorly understood in animal cells. We have previously shown that expression of Rab8 promotes the formation of new cell surface domains through reorganization of actin and microtubules. To unravel the function of Rab8, we used the yeast two-hybrid system to search for potential Rab8-specific activators. We identified a coil-coiled protein (Rabin8), homologous to the rat Rabin3 that stimulated nucleotide exchange on Rab8 but not on Rab3A and Rab5. Furthermore, we show that rat Rabin3 has exchange activity on Rab8 but not on Rab3A, supporting the view that rat Rabin3 is the rat equivalent of human Rabin8. Rabin8 localized to the cortical actin and expression of Rabin8 resulted in remodeling of actin and the formation of polarized cell surface domains. Activation of PKC by phorbol esters enhanced translocation of both Rabin8 and Rab8-specific vesicles to the outer edge of lamellipodial structures. Moreover, coexpression of Rabin8 with dominant negative Rab8 (T22N) redistributes Rabin8 from cortical actin to Rab8-specific vesicles and promotes their polarized transport to cell protrusions. The C-terminal region of Rabin8 plays an essential role in this transport. We propose that Rabin8 is a Rab8-specific activator that is connected to processes that mediate polarized membrane traffic to dynamic cell surface structures.
Proteasome Regulates the Delivery of LDL Receptor-related Protein into the Degradation Pathway
Authors: Melman Lora , Geuze Hans J. , Li Yonghe , McCormick Lynn M. , van Kerkhof Peter , Strous Ger J. , Schwartz Alan L. , Bu Guojun
Published: September 2002

The low-density lipoprotein receptor (LDLR)-related protein (LRP) is a multiligand endocytic receptor that has broad cellular and physiological functions. Previous studies have shown that both tyrosine-based and di-leucine motifs within the LRP cytoplasmic tail are responsible for mediating its rapid endocytosis. Little is known, however, about the mechanism by which LRP is targeted for degradation. By examining both endogenous full-length and a minireceptor form of LRP, we found that proteasomal inhibitors, MG132 and lactacystin, prolong the cellular half-life of LRP. The presence of proteasomal inhibitors also significantly increased the level of LRP at the cell surface, suggesting that the delivery of LRP to the degradation pathway was blocked at a compartment from which recycling of the receptor to the cell surface still occurred. Immunoelectron microscopy analyses demonstrated a proteasomal inhibitor-dependent reduction in LRP minireceptor within both limiting membrane and internal vesicles of the multivesicular bodies, which are compartments that lead to receptor degradation. In contrast to the growth hormone receptor, we found that the initial endocytosis of LRP minireceptor does not require a functional ubiquitin–proteasome system. Finally, using truncated cytoplasmic mutants of LRP minireceptors, we found that a region of 19 amino acids within the LRP tail is required for proteasomal regulation. Taken together our results provide strong evidence that the cellular turnover of a cargo receptor, i.e., LRP, is regulated by the proteasomal system, suggesting a broader function of the proteasome in regulating the trafficking of receptors into the degradation pathway.
Pkh1 and Pkh2 Differentially Phosphorylate and Activate Ypk1 and Ykr2 and Define Protein Kinase Modules Required for Maintenance of Cell Wall Integrity
Authors: Roelants Françoise M. , Torrance Pamela D. , Bezman Natalie , Thorner Jeremy
Published: September 2002

Saccharomyces cerevisiae Pkh1 and Pkh2 are functionally redundant homologs of mammalian protein kinase, phosphoinositide-dependent protein kinase-1. They activate two closely related, functionally redundant enzymes, Ypk1 and Ykr2 (homologs of mammalian protein kinase, serum- and glucocorticoid-inducible protein kinase). We found that Ypk1 has a more prominent role than Ykr2 in mediating their shared essential function. Considerable evidence demonstrated that Pkh1 preferentially activates Ypk1, whereas Pkh2 preferentially activates Ykr2. Loss of Pkh1 (but not Pkh2) reduced Ypk1 activity; conversely, Pkh1 overexpression increased Ypk1 activity more than Pkh2 overexpression. Loss of Pkh2 reduced Ykr2 activity; correspondingly, Pkh2 overexpression increased Ykr2 activity more than Pkh1 overexpression. When overexpressed, a catalytically active C-terminal fragment (kinase domain) of Ypk1 was growth inhibitory; loss of Pkh1 (but not Pkh2) alleviated toxicity. Loss of Pkh2 (but not Pkh1) exacerbated the slow growth phenotype of aypk1Δ strain. This Pkh1-Ypk1 and Pkh2-Ykr2 dichotomy is not absolute because all double mutants (pkh1Δ ypk1Δ, pkh2Δ ypk1Δ, pkh1Δ ykr2Δ, and pkh2Δ ykr2Δ) were viable. Compartmentation contributes to selectivity because Pkh1 and Ypk1 were located exclusively in the cytosol, whereas Pkh2 and Ykr2 entered the nucleus. At restrictive temperature,ypk1-1tsykr2Δ cells lysed rapidly, but not in medium containing osmotic support. Dosage and extragenic suppressors were selected. Overexpression of Exg1 (major exoglucanase), or loss of Kex2 (endoprotease involved in Exg1 processing), rescued growth at high temperature. Viability was also maintained by PKC1 overexpression or an activated allele of the downstream protein kinase (BCK1-20). Conversely, absence of Mpk1 (distal mitogen-activated protein kinase of thePKC1 pathway) was lethal inypk1-1tsykr2Δ cells. Thus, Pkh1-Ypk1 and Pkh2-Ykr2 function in a novel pathway for cell wall integrity that acts in parallel with the Pkc1-dependent pathway.