bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics of kefir prepared with different
grain[ratio ]milk ratios
Authors: GARROTE GRACIELA L. , ABRAHAM ANALÍA G. , DE ANTONI GRACIELA L.
Published: July 2002

Kefir is a traditional fermented milk originating
many centuries ago in the
Caucasian mountains. It is produced by fermentative
activity of ‘kefir grains’
consisting mainly of lactococci, lactobacilli and yeasts
in a protein–polysaccharide
matrix. The grains contain a relatively stable and specific
balance of microorganisms
which exist in a complex symbiotic relationship. The grains
grow in the process of
kefir making only from pre-existing grains (Saloff-Coste,
1996). When kefir grains are
allowed to grow in milk, microorganisms are shed from the
grains into milk where
they continue to multiply with the production of acid,
flavour and physicochemical changes.

The traditional method of kefir making is currently by
adding kefir grains
directly as starter to milk that has been pasteurized and
cooled to 20–25°C. After a
period of fermentation lasting ∼24 h, the grains are
removed by filtration and the
beverage is ready for consumption (Saloff-Coste, 1996). Kefir
from which the grains
have been removed may be used as starter. However, this
fermented milk cannot be
used for subsequent inoculations to make an acceptable
product, because the original
balance of microorganisms has been disrupted (Kroger, 1993).

The complex microbiological composition of kefir grains
explains why it is
difficult to obtain starter with the optimal and constant
composition necessary for
a regular production of kefir of standard quality
(Koroleva, 1988a). Studies have
been undertaken to establish cultivation
conditions[ratio ]grain[ratio ]milk ratio, cultivation
temperature, period of time and conditions prior to
separation of grains from the
fermented milk, shaking conditions for agitation of milk
with the grains in the course
of fermentation, washing of kefir grains and so on. All
these factors influence the
microflora of the kefir starter and fermented milk. There
are no rules about
household manufacture of kefir. Different reports
indicate a wide range of grain[ratio ]milk
ratios for kefir making. Bottazzi & Bianchi (1980),
Marshall & Cole (1985), Merin &
Rosenthal (1986), Mann (1989), Hosono et al.
(1990) and Kroger (1993) employed
20–50 g/l while Koroleva (1988a)
employed 20–100 g kefir grain/l and Marshall
et al. (1984) and Neve (1992) 50–100 g/l.
Rea et al. (1996) used 1 g kefir grain/l as starter
and 200 g starter in the form of kefir grains is
recommended by Hansen for the
fermentation of 1 l milk (Marshall & Cole, 1985). A
critical control point in kefir
manufacture to obtain a product with constant quality is
the standardization of the
kefir grain[ratio ]milk ratio. Koroleva (1988b) claimed
that it is better to use kefir grains
as starter for kefir production and, at the same time, to
decrease the amount of inoculum.

The purpose of this study was to evaluate the effects
of changes in the kefir
grain[ratio ]milk ratio (quantity of kefir grains inoculated
into the milk) on microflora
composition, acidity, apparent viscosity and carbon dioxide
content of fermented milk.
Influence of thermal and other manufacturing stresses on retinol
isomerization in milk and dairy products
Authors: PANFILI GIANFRANCO , MANZI PAMELA , PIZZOFERRATO LAURA
Published: July 2002

An analytical procedure, based upon HPLC, has been used to determine

the degree of isomerization of retinol (vitamin A) in various dairy products.
In raw
milks, which are not subjected to thermal processing, there was no conversion
of the
predominant all-trans-isomers to cis-isomers in
samples from various species.
Pasteurized milks with mild heat treatment (high quality milk) had an average

13-cis[ratio ]all-trans ratio of 2·6%,
while pasteurized milk treated for 15 s at temperatures
ranging from 72 to 76°C had an average ratio of 6·4%. Milk subjected
to more severe
heat treatments had a higher degree of isomerization (UHT milk, 15·7%;
sterilized
milk, 33·5%), consistent with increased thermal conversion of the
retinol isomers. In
pasteurized and UHT cream, the increase in 13-cis-isomer was also
a consequence of
heat treatment (pasteurized cream, 3·0%; UHT cream, 14·4%).

The presence of cis
isomers in fermented milk suggests that fermentation processes, directly
or
indirectly, can induce cis–trans isomerization.

In the cheeses analysed, the extent of
retinol isomerization ranged from 7·6 to 35·0%. Our
results confirm the importance
of individual isomers in evaluating the vitamin A status of dairy products.
Numerical investigation of transitional and weak turbulent flow past a sphere
Authors: TOMBOULIDES ANANIAS G. , ORSZAG STEVEN A.
Published: July 2002

This work reports results of numerical simulations of viscous incompressible flow past
a sphere. The primary objective is to identify transitions that occur with increasing
Reynolds number, as well as their underlying physical mechanisms. The numerical method
used is a mixed spectral element/Fourier spectral method developed
for applications involving both Cartesian and cylindrical coordinates. In cylindrical
coordinates, a formulation, based on special Jacobi-type polynomials, is used close
to the axis of symmetry for the efficient treatment of the ‘pole’ problem. Spectral
convergence and accuracy of the numerical formulation are verified. Many of the
computations reported here were performed on parallel computers. It was found
that the first transition of the flow past a sphere is a linear one and leads to a
three-dimensional steady flow field with planar symmetry, i.e. it is of the ‘exchange of
stability’ type, consistent with experimental observations on falling spheres and linear
stability analysis results. The second transition leads to a single-frequency periodic
flow with vortex shedding, which maintains the planar symmetry observed at lower
Reynolds number. As the Reynolds number increases further, the planar symmetry is
lost and the flow reaches a chaotic state. Small scales are first introduced in the flow
by Kelvin–Helmholtz instability of the separating cylindrical shear layer; this shear
layer instability is present even after the wake is rendered turbulent.
Computations of fully nonlinear three-dimensional wave–wave and wave–body interactions.
Part 2. Nonlinear waves and forces on a body
Authors: LIU YUMING , XUE MING , YUE DICK K. P.
Published: July 2002

The mixed-Eulerian–Lagrangian method using high-order boundary elements, described
in Xue et al. (2001) for the simulation of fully nonlinear three-dimensional
wave–wave and wave–body interactions, is here extended and applied to the study
of two nonlinear three-dimensional wave–body problems: (a) the development of
bow waves on an advancing ship; and (b) the steep wave diffraction and nonlinear
high-harmonic loads on a surface-piercing vertical cylinder. For (a), we obtain
convergent steady-state bow wave profiles for a flared wedge, and the Wigley and
Series 60 hulls. We compare our predictions with experimental measurements and
find good agreement. It is shown that upstream influence, typically not accounted
for in quasi-two-dimensional theory, plays an important role in bow wave prediction
even for fine bows. For (b), the primary interest is in the higher-harmonic ‘ringing’
excitations observed and quantified in experiments. From simulations, we obtain fully
nonlinear steady-state force histories on the cylinder in incident Stokes waves. Fourier
analysis of such histories provides accurate predictions of harmonic loads for which
excellent comparisons to experiments are obtained even at third order. This confirms
that ‘ringing’ excitations are directly a result of nonlinear wave diffraction.
Noise sources in a low-Reynolds-number turbulent jet at Mach 0.9
Authors: FREUND JONATHAN B.
Published: July 2002

The mechanisms of sound generation in a Mach 0.9, Reynolds number 3600 turbulent
jet are investigated by direct numerical simulation. Details of the numerical method
are briefly outlined and results are validated against an experiment at the same flow
conditions (Stromberg, McLaughlin & Troutt 1980). Lighthill's theory is used to define
a nominal acoustic source in the jet, and a numerical solution of Lighthill's equation
is compared to the simulation to verify the computational procedures. The acoustic
source is Fourier transformed in the axial coordinate and time and then filtered in
order to identify and separate components capable of radiating to the far field. This
procedure indicates that the peak radiating component of the source is coincident
with neither the peak of the full unfiltered source nor that of the turbulent kinetic
energy. The phase velocities of significant components range from approximately 5%
to 50% of the ambient sound speed which calls into question the commonly made
assumption that the noise sources convect at a single velocity. Space–time correlations
demonstrate that the sources are not acoustically compact in the streamwise direction
and that the portion of the source that radiates at angles greater than 45° is stationary.
Filtering non-radiating wavenumber components of the source at single frequencies
reveals that a simple modulated wave forms for the source, as might be predicted by
linear stability analysis. At small angles from the jet axis the noise from these modes
is highly directional, better described by an exponential than a standard Doppler
factor.
Statistical sand wave dynamics in one-directional water flows
Authors: NIKORA VLADIMIR I. , SUKHODOLOV ALEXANDER N. , ROWINSKI PAWEL M.
Published: July 2002

Moving sand waves and the overlying tubulent flow were

measured on the Wilga River

in Poland, and the Tirnava Mica and Buzau Rivers in Romania. Bottom elevations
and

flow velocities were measured at six points simultaneously by multi-channel
measuring

systems. From these data, the linear and two-dimensional sections of the

three-dimensional correlation and structure functions and various projections
of

sand wave three-dimensional spectra were investigated.

It was found that the longitudinal wavenumber spectra of the sand waves
in the

region of large wavenumbers followed Hino's −3 law

(S(Kx)

∝K−3x)

quite satisfactorily, confirming the theoretical predictions of Hino

(1968) and Jain & Kennedy

(1974). However, in contrast to Hino (1968), the sand wave frequency spectrum
in the

high-frequency region was approximated by a power function with the exponent

−2, while in the lower-frequency region this exponent is close to
−3.

A dispersion relation for sand waves has been investigated from analysis
of

structure functions, frequency spectra and the cross-correlation

functions method. For

wavelengths less than 0.15–0.25 of the flow depth, their

propagation velocity C is

inversely proportional to the wavelength λ. When the wavelengths
of spectral

components are as large as 3–4 times the flow depth, no

dispersion occurs. These results

proved to be in good qualitative agreement with the theoretical dispersion
relation

derived from the potential-flow-based analytical models (Kennedy 1969;
Jain &

Kennedy 1974). We also present another, physically-based, explanation of
this

phenomenon, introducing two types of sand movement in the form of sand
waves. The

first type (I) is for the region of large wavenumbers (small wavelengths)
and

the second one (II) is for the region of small wavenumbers (large wavelengths).

The small sand waves move due to the motion of individual sand particles
(type I,

C∝λ−1) while

larger sand waves propagate as a result of the motion of smaller waves
on their

upstream slopes (type II, C∝λ0). Like

the sand particles in the first type, these smaller

waves redistribute sand from upstream slopes to downstream ones. Both types
result

in sand wave movement downstream but with a different propagation velocity.

The main characteristics of turbulence, as well as the quantitative
values

characterizing the modulation of turbulence by sand waves, are also presented.
Premixed flame–wall interaction in a turbulent

channel flow: budget for the flame surface

density evolution equation and modelling
Authors: BRUNEAUX G. , POINSOT T. , FERZIGER J. H.
Published: July 2002

Turbulent premixed flame propagation in the vicinity of a

wall is studied using a

three-dimensional constant-density simulation of flames propagating in

a channel. The

influence of the walls is investigated in terms of the flamelet approach,

where flamelet

speed and flame surface density transport are used to describe the flame.
The walls

have constant temperature and lead to flamelet quenching for

sufficiently small wall–flame distances. Starting from the

exact evolution equation for the surface density of

propagating interfaces (Trouvé & Poinsot 1994; Candel &

Poinsot 1990; Pope 1988), a

budget for the flame surface density equation is presented before,

during, and after the

interaction with the wall. Before the flame interacts with the wall,

flame propagation

is controlled by a balance between surface production and annihilation.
During the

interaction, high flame surface density gradients near the wall are responsible
for

the predominance of the transport terms. Closures of all terms of the flame
surface

density equation are proposed. These models are based on flamelet ideas
and take into

account wall effects. Enthalpy loss through the wall affects flamelet speed,
flamelet

annihilation and flame propagation. Decrease of turbulent scales

near the wall affects

turbulent diffusion and flame strain. This model is compared to DNS results
using

two types of tests: (i) a priori tests, where individual

terms of the modelled flame

surface density equation are compared to the terms of the exact interface
density

propagation equation, calculated with the DNS; (ii) a posteriori

tests, where the final

model is used to obtain total reaction rate, mean fuel mass fraction,

heat flux at the

wall and fuel mass fraction at the wall in the configuration used in the
DNS. For

both types of tests the model compares well with the DNS results.
Break-up and atomization of a round water jet by
a high-speed annular air jet
Authors: LASHERAS J. C. , VILLERMAUX E. , HOPFINGER E. J.
Published: July 2002

The near- and far-field break-up and atomization of a water jet
by a high-speed
annular air jet are examined by means of high-speed flow visualizations
and phase
Doppler particle sizing techniques. Visualization of the jet's near
field and
measurements of the frequencies associated with the gas–liquid interfacial
instabilities
are used to study the underlying physical mechanisms involved in the primary
break-up
of the water jet. This process is shown to consist of the stripping of
water sheets,
or ligaments, which subsequently break into smaller lumps or drops. An
entrainment
model of the near-field stripping of the liquid is proposed, and shown
to describe the
measured liquid shedding frequencies. This simplified model explains qualitatively
the
dependence of the shedding frequency on the air/water momentum ratio
in both
initially laminar and turbulent water jets. The role of the secondary liquid
break-up in
the far-field atomization of the water jet is also investigated, and an
attempt is made
to apply the classical concepts of local isotropy to explain qualitatively
the
measurement of the far-field droplet size distribution and its dependence
on the water
to air mass and momentum ratios. Models accounting for the effect of the
local
turbulent dissipation rate in the gas on both the break-up and coalescence
of the
droplets are developed and compared with the measurements of the variation
of the
droplet size along the jet's centreline. The total flux of kinetic
energy supplied by the
gas per unit total mass of the spray jet was found to be the primary parameter

determining the secondary break-up and coalescence of the droplets in the
far field.
Cavitation and the state of stress in a flowing liquid
Authors: JOSEPH DANIEL D.
Published: July 2002

The problem of the inception of cavitation is formulated in terms
of a comparison of
the breaking strength or cavitation threshold at each point in a liquid
sample with the
principal stresses there. A criterion of maximum tension is proposed which
unifies the
theory of cavitation, the theory of maximum tensile strength of liquid
filaments and
the theory of fracture of amorphous solids. Liquids at atmospheric pressure
which
cannot withstand tension will cavitate when and where tensile stresses
due to motion
exceed one atmosphere. A cavity will open in the direction of the maximum
tensile
stress which is 45° from the plane of shearing in pure shear of a Newtonian
fluid.
Experiments which support these ideas are discussed and some new experiments
are
proposed.
Direct analysis of particulate suspensions with
inertia using the discrete Boltzmann equation
Authors: AIDUN CYRUS K. , LU YANNAN , DING E.-JIANG
Published: July 2002

An efficient and robust computational method, based on the lattice-Boltzmann

method, is presented for analysis of impermeable solid particle(s) suspended
in fluid
with inertia. In contrast to previous lattice-Boltzmann approaches, the
present method
can be used for any solid-to-fluid density ratio. The details of the numerical
technique
and implementation of the boundary conditions are presented. The accuracy

and robustness of the method is demonstrated by simulating the flow over
a circular
cylinder in a two-dimensional channel, a circular cylinder in simple shear
flow,
sedimentation of a circular cylinder in a two-dimensional channel, and
sedimentation
of a sphere in a three-dimensional channel. With a solid-to-fluid density
ratio
close to one, new results from two-dimensional and three-dimensional computational

analysis of dynamics of an ellipse and an ellipsoid in a simple shear flow,
as well as
two-dimensional and three-dimensional results for sedimenting ellipses
and prolate
spheroids, are presented.
Cavitation erosion by single laser-produced bubbles
Authors: PHILIPP A. , LAUTERBORN W.
Published: July 2002

In order to elucidate the mechanism of cavitation erosion, the
dynamics of a single
laser-generated cavitation bubble in water and the resulting surface damage
on a
flat metal specimen are investigated in detail. The characteristic effects
of bubble
dynamics, in particular the formation of a high-speed liquid jet and the
emission of
shock waves at the moment of collapse are recorded with high-speed photography

with framing rates of up to one million frames/s. Damage is observed
when the
bubble is generated at a distance less than twice its maximum radius from
a solid
boundary (γ=2, where γ=s/Rmax,

s is the distance between the boundary and
the bubble centre at the moment of formation and Rmax

is the maximum bubble
radius). The impact of the jet contributes to the damage only at small
initial distances
(γ[les ]0.7). In this region, the impact velocity rises to 83 m s−1,

corresponding to a water hammer pressure of about 0.1 GPa, whereas at γ>1,

the impact velocity is smaller than 25 m s−1. The largest
erosive
force is caused by the collapse of a bubble
in direct contact with the boundary, where pressures of up to several GPa
act on
the material surface. Therefore, it is essential for the damaging effect
that bubbles are
accelerated towards the boundary during the collapse phases due to Bjerknes
forces.
The bubble touches the boundary at the moment of second collapse when γ<2
and
at the moment of first collapse when γ<1. Indentations on an aluminium
specimen
are found at the contact locations of the collapsing bubble. In the range
γ=1.7 to 2,
where the bubble collapses mainly down to a single point, one pit below
the bubble
centre is observed. At γ[les ]1.7, the bubble shape has become toroidal,
induced by
the jet flow through the bubble centre. Corresponding to the decay of this
bubble
torus into multiple tiny bubbles each collapsing separately along the circumference

of the torus, the observed damage is circular as well. Bubbles in the ranges
γ[les ]0.3
and γ=1.2 to 1.4 caused the greatest damage. The overall diameter
of the damaged
area is found to scale with the maximum bubble radius. Owing to the possibility
of
generating thousands of nearly identical bubbles, the cavitation resistance
of even
hard steel specimens can be tested.
Evolution of a wave packet into vortex loops in a
laminar separation bubble
Authors: WATMUFF JONATHAN H.
Published: July 2002

A laminar boundary layer develops in a favourable pressure gradient where the
velocity profiles asymptote to the Falkner & Skan similarity solution. Flying-hot-wire
measurements show that the layer separates just downstream of a subsequent region of
adverse pressure gradient, leading to the formation of a thin separation bubble. In an
effort to gain insight into the nature of the instability mechanisms, a small-magnitude
impulsive disturbance is introduced through a hole in the test surface at the pressure
minimum. The facility and all operating procedures are totally automated and phase-averaged data are acquired on unprecedently large and spatially dense measurement
grids. The evolution of the disturbance is tracked all the way into the reattachment
region and beyond into the fully turbulent boundary layer. The spatial resolution of
the data provides a level of detail that is usually associated with computations.

Initially, a wave packet develops which maintains the same bounded shape and
form, while the amplitude decays exponentially with streamwise distance. Following
separation, the rate of decay diminishes and a point of minimum amplitude is reached,
where the wave packet begins to exhibit dispersive characteristics. The amplitude then
grows exponentially and there is an increase in the number of waves within the packet.
The region leading up to and including the reattachment has been measured with a
cross-wire probe and contours of spanwise vorticity in the centreline plane clearly show
that the wave packet is associated with the cat's eye pattern that is a characteristic of
Kelvin–Helmholtz instability. Further streamwise development leads to the formation
of roll-ups and contour surfaces of vorticity magnitude show that they are three-dimensional. Beyond this point, the behaviour is nonlinear and the roll-ups evolve
into a group of large-scale vortex loops in the vicinity of the reattachment. Closely
spaced cross-wire measurements are continued in the downstream turbulent boundary
layer and Taylor's hypothesis is applied to data on spanwise planes to generate three-dimensional velocity fields. The derived vorticity magnitude distribution demonstrates
that the second vortex loop, which emerges in the reattachment region, retains its
identity in the turbulent boundary layer and it persists until the end of the test section.
Direct numerical simulation of ‘short’ laminar
separation bubbles with turbulent reattachment
Authors: ALAM M. , SANDHAM N. D.
Published: July 2002

Direct numerical simulation of the incompressible Navier-Stokes equations is used
to study flows where laminar boundary-layer separation is followed by turbulent
reattachment forming a closed region known as a laminar separation bubble. In
the simulations a laminar boundary layer is forced to separate by the action of
a suction profile applied as the upper boundary condition. The separated shear
layer undergoes transition via oblique modes and Λ-vortex-induced breakdown and
reattaches as turbulent flow, slowly recovering to an equilibrium turbulent boundary
layer. Compared with classical experiments the computed bubbles may be classified
as ‘short’, as the external potential flow is only affected in the immediate vicinity of
the bubble. Near reattachment budgets of turbulence kinetic energy are dominated
by turbulence events away from the wall. Characteristics of near-wall turbulence only
develop several bubble lengths downstream of reattachment. Comparisons are made
with two-dimensional simulations which fail to capture many of the detailed features
of the full three-dimensional simulations. Stability characteristics of mean flow profiles
are computed in the separated flow region for a family of velocity profiles generated
using simulation data. Absolute instability is shown to require reverse flows of the
order of 15–20%. The three-dimensional bubbles with turbulent reattachment have
maximum reverse flows of less than 8% and it is concluded that for these bubbles
the basic instability is convective in nature.
Nonlinear instability of plane liquid sheets
Authors: JAZAYERI SEYED A. , LI XIANGUO
Published: July 2002

A nonlinear stability analysis has been carried out for plane liquid sheets moving
in a gas medium at rest by a perturbation expansion technique with the initial
amplitude of the disturbance as the perturbation parameter. The first, second and
third order governing equations have been derived along with appropriate initial and
boundary conditions which describe the characteristics of the fundamental, and the
first and second harmonics. The results indicate that for an initially sinusoidal sinuous
surface disturbance, the thinning and subsequent breakup of the liquid sheet is due
to nonlinear effects with the generation of higher harmonics as well as feedback into
the fundamental. In particular, the first harmonic of the fundamental sinuous mode is
varicose, which causes the eventual breakup of the liquid sheet at the half-wavelength
interval of the fundamental wave. The breakup time (or length) of the liquid sheet is
calculated, and the effect of the various flow parameters is investigated. It is found
that the breakup time (or length) is reduced by an increase in the initial amplitude
of disturbance, the Weber number and the gas-to-liquid density ratio, and it becomes
asymptotically insensitive to the variations of the Weber number and the density
ratio when their values become very large. It is also found that the breakup time (or
length) is a very weak function of the wavenumber unless it is close to the cut-off
wavenumbers.
A scalar subgrid model with flow structure for
large-eddy simulations of scalar variances
Authors: FLOHR P. , VASSILICOS J. C.
Published: July 2002

A new model to simulate passive scalar fields in large-eddy simulations of turbulence
is presented. The scalar field is described by clouds of tracer particles and the subgrid
contribution of the tracer displacement is modelled by a kinematic model which obeys
Kolmogorov's inertial-range scaling, is incompressible and incorporates turbulent-like
flow structure of the turbulent small scales. This makes it possible to study the scalar
variance field with inertial-range effects explicitly resolved by the kinematic subgrid
field while the LES determines the value of the Lagrangian integral time scale TL.
In this way, the modelling approach does not rely on unknown Lagrangian input
parameters which determine the absolute value of the scalar variance.

The mean separation of particle pairs displays a well-defined Richardson scaling
in the inertial range, and we find that the Richardson constant
GΔ ≈ 0.07 which is
small compared to the value obtained from stochastic models with the same TL. The
probability density function of the separation of particle pairs is found to be highly
non-Gaussian in the inertial range of times and for long times becomes Gaussian.
We compute the scalar variance field for an instantaneous line source and find good
agreement with experimental data.
The Earth's plasma sheet as a laboratory for
flow turbulence in high-β MHD
Authors: BOROVSKY JOSEPH E. , ELPHIC RICHARD C. , FUNSTEN HERBERT O. , THOMSEN MICHELLE F.
Published: July 2002

The bulk flows and magnetic-field fluctuations of the plasma sheet
are
investigated using single-point measurements from the ISEE-2 Fast Plasma
Experiment and fluxgate magnetometer. Ten several-hour-long intervals of
continuous data (with 3 s and 12 s time resolution) are analysed. The plasma-sheet
flow appears to be strongly ‘turbulent’ (i.e. the flow is
dominated by
fluctuations that are unpredictable, with rms velocities[Gt ]mean velocities
and
with field fluctuations≈mean fields). The flow velocities are typically
sub-Alfvénic. The flow-velocity probability distribution
P(v) is constructed, and is
found to be well fitted by exponential functions. Autocorrelation functions
[Ascr ](τ) are constructed, and the autocorrelation times τcorr
for the flow velocities
are found to be about 2 min. From the flow measurements, an estimate of
the
mixing length in the plasma sheet is produced, yielding
Lmix≈2 Earth radii;
correspondingly, the plasma-sheet material appears to be well mixed in
density
and temperature. An eddy viscosity for the plasma sheet is also estimated.
Power spectra, which are constructed from the v(t) and B(t)
time series, have
portions that are power laws with spectral indices that are near the range
of
those expected for turbulence theories. The plasma sheet may provide a
laboratory for the study of turbulence in parameter regimes different from
that
of solar-wind turbulence: the plasma sheet is a β[Gt ]1, hot-ion plasma,
and the
turbulence may be strongly driven rather than well developed. The turbulent
nature of the flow and the disordered nature of the magnetic field have
implications for the transport of plasma-sheet material, for the penetration
of
the solar-wind electric field into the plasma sheet, and for the calculation
of
particle orbits in the magnetotail.
The trouble with entropy
Authors: de HAAN M. , GEORGE C. D.
Published: July 2002

An understanding of the mechanisms leading to the symmetry breaking
of the
dynamical description of a large system with respect to the direction of
time is
necessary, but not sufficient to ensure the finding of a functional of
the state of the
system that would satisfy the requirements placed by the Second Law of

Thermodynamics upon the non-equilibrium entropy S.
Diet of the common wolffish Anarhichas lupus in the North Sea
Authors: Liao Yih-Yia , Lucas Martyn C.
Published: July 2002

The diet of common wolffish Anarhichas lupus from the North Sea is described, from a total of 143 wolffish stomachs, of which 112 contained food. The main prey were crustaceans and molluscs, together representing almost 70% of diet by relative frequency of occurrence in stomachs. Wolffish >55 cm preferred polychaetes and gastropods while wolffish <55 cm preferred sea urchins and brittle stars. The occurrence of empty stomachs was significantly less in spring than in summer or in autumn/winter. Meal size was lowest in winter and highest in spring. These data reflect a period of low food intake in winter during spawning and tooth replacement, followed by a recovery feeding episode in spring.
No effect of a parasite on reproduction in stickleback males: a laboratory artefact?
Authors: CANDOLIN U. , VOIGT H.-R.
Published: July 2002

Experiments are often carried out in the laboratory under artificial conditions. Although this can control for confounding factors, it may eliminate important factors that under natural conditions mediate the interaction under investigation. Here, we show that different results can be gained in the field and in the laboratory regarding host–parasite interaction. In the field, courting three-spined stickleback males, Gasterosteus aculeatus, were less often infected with plerocercoids of a cestode tapeworm, Schistocephalus solidus, than shoaling males. However, when a random sample of males was allowed to nest and court females in individual aquaria in the laboratory, both uninfected and infected males built nests and courted females. Moreover, while the few infected males that courted females in the field expressed less red nuptial coloration than uninfected courting males, there was no difference in redness between infected and uninfected males in the laboratory. We argue that the different results gained in the field and in the laboratory are due to differences in the cost of reproduction, due to differences in the resource pool of the males. The favourable conditions in the laboratory exclude factors such as predation risk, social interactions, and fluctuating environmental conditions that may use up resources in the field and mediate the effect of the parasite.
Genetic variation in sympatric Ascaris populations from
humans and pigs in China
Authors: PENG WEIDONG , ANDERSON T. J. C. , ZHOU XIANMIN , KENNEDY M. W.
Published: July 2002

It has recently been shown using genetic markers that Ascaris

in humans and pigs in Central America comprise
reproductively isolated populations. We present a similar analysis for
a
region of China in which close association between
pigs and humans has been the norm for thousands of years, and agricultural

practices will result in frequent exposure to
eggs from both sources. DNA fragments from selected regions of mitochondrial

and ribosomal DNA were amplified by
PCR and allelic forms identified following digestion with a panel of
restriction enzymes, using DNA from a total of 115
individual worms from both people and pigs from 2 neighbouring villages.

Significant frequency differences in both
mtDNA haplotypes and the rDNA spacer were found between the 2 host-associated

populations, indicating that they
represented reproductively isolated populations. Mitochondrial haplotype

frequencies were different from those observed
in Guatemala and also from other Asian Ascaris populations,
suggesting low levels of gene flow between populations.
However, we found no evidence for significant heterogeneity in the
genetic composition of Ascaris infrapopulations in
either humans or pigs, possibly indicative of agricultural practices
in China which have resulted in a random distribution
of alleles within the parasite populations.
Resistance of Phlebotomus papatasi to infection with
Leishmania donovani is modulated by components of the
infective bloodmeal
Authors: SCHLEIN Y. , JACOBSON R. L.
Published: July 2002

The circumstances which permit the establishment of Leishmania
infections in sandflies were investigated by altering the
growth conditions for L. donovani parasites in the unsuitable
vector Phlebotomus papatasi. Only 5·0% of the sandflies

harboured a few parasites 3 days after feeding on promastigotes in defibrinated
blood. Heparinized blood or the addition
of trypsin inhibitor to the meals allowed persistence of infections (day
6) in 9·9% and 25·8% of the flies respectively. Meals
of erythrocytes, saline and amastigotes produced 44·4% fly infection
on day 6, while similar promastigote-initiated
infections remained in 70·3% of the flies. Proteolytic activities
in the guts of sandflies fed on the above meals without
parasites, were the highest after defibrinated bloodmeals. Erythrocytes
with saline decreased the maximal alkaline protease
level from 20·8 U to 13·5 U/fly; that of trypsin from
3·9 U to 1·8 U/fly and that of the aminopeptidase from
5·5 U to
3·9 U/fly. After meals of heparinized blood, the maximal alkaline
protease activity (12·0 U/fly) was also much lower than
after defibrinated blood-feeding. The different diets which resulted in
comparatively low enzymatic activities, including
blood with trypsin inhibitor, also promoted the survival of infections.
This implies that the proteolytic activity in the
sandfly gut modulates the vector susceptibility.
Twelve microsatellite markers for characterization of
Plasmodium falciparum from finger-prick blood samples
Authors: ANDERSON T. J. C. , SU XIN-ZHUAN , BOCKARIE M. , LAGOG M. , DAY K. P.
Published: July 2002

Multiple, selectively neutral genetic markers are the most appropriate tools for analysis of parasite population structure
and epidemiology, but yet existing methods for characterization of malaria field samples utilize a limited number of antigen
encoding genes, which appear to be under strong selection. We describe protocols for characterization of 12 microsatellite
markers from finger-prick blood samples infected with Plasmodium falciparum. A two-step, heminested strategy was used
to amplify all loci, and products were visualized by fluorescent end-labelling of internal primers. This procedure allows
amplification from low levels of template, while eliminating the problem of spurious products due to primer carry over
from the primary round of PCR. The loci can be conveniently multiplexed, while accurate sizing and quantification of
PCR products can be automated using the GENOTYPER software. The primers do not amplify co-infecting malaria species
such as P. vivax and P. malariae. To demonstrate the utility of these markers, we characterized 57 infected finger-prick
blood samples from the village of Mebat in Papua New Guinea for all 12 loci, and all samples were genotyped a second
time to measure reproducibility. Numbers of alleles per locus range from 4 to 10 in this population, while heterozygosities
range from 0·21 to 0·87. Reproducibility (measured as concordance between predominant alleles detected in replicate
samples) ranged from 92 to 98% for the 12 loci. The composition of PCR products from infections containing multiple
malaria clones could also be defined using strict criteria and scored in a highly repeatable manner.
Mitochondrial genes of Schistosoma mansoni
Authors: BLAIR D. , LE T. H. , DESPRÉS L. , McMANUS D. P.
Published: July 2002

Two clones, totalling 8068 bp and spanning over half of the coding region of the mitochondrial genome of Schistosoma
mansoni, have been sequenced. Complete sequences are presented of the large and small ribosomal RNA subunits, CO2,
ND3, ND4, ND6 and ATPase 6 genes. Incomplete sequences were found for the CO1, ND2 and CytB genes. At least
10 tRNAs were also detected and alternative structures for some of these discussed. The gene order of S. mansoni is unique
and differs from that of Fasciola hepatica, the only other trematode for which any information is available.
Vairimorpha imperfecta n.sp., a microsporidian exhibiting
an abortive octosporous sporogony in Plutella xylostella L.
(Lepidoptera: Yponomeutidae)
Authors: CANNING E. U. , CURRY A. , CHENEY S. , LAFRANCHI-TRISTEM N. J. , HAQUE M. A.
Published: July 2002

The microsporidian genus Nosema is characterized by development in direct control with host cell cytoplasm, diplokaryotic
nuclei throughout development and disporous sporogony. The genus Vairimorpha exhibits the same features plus an
octoporous sporogony producing uninucleate spores in a sporophorous vesicle. A microsporidium from diamondback
moth, Plutella xylostella, falls between Nosema and Vairimorpha in that it initiates but fails to complete the octosporous
sequence in this host. The name Vairimorpha imperfecta n.sp. is proposed. Merogony is mainly by formation of buds from
multinucleate meronts, the buds remaining attached in chains. Diplokaryotic spores measure 4·3×2·0 μm (fresh) and
have 15·5 coils of the polar tube in 1 rank. The octosporous sporogony is aborted owing to irregular formation of nuclear
spindles, incomplete cytoplasmic fission and bizarre deposition of electron-dense episporontal secretions. Phylogenetic
analyses of the sequences of the small subunit rRNA genes of V. imperfecta and of several Nosema and Vairimorpha spp.
place V. imperfecta in a clade with Nosema spp. from Lepidoptera rather than in the clade containing the more typical
species of Vairimorpha. It is suggested that the ancestors of the Vairimorpha/Nosema complex of species exhibited both
disporous and octosporous sporogonies, as does the type species of Vairimorpha, Vairimorpha necatrix. It would follow
that true Nosema spp. have lost the ability to express an octosporous sequence and that V. imperfecta is in the process of
losing it. It is proposed that the genera Nosema and Vairimorpha be placed in the same family Nosematidae Labbé 1899,
rather than in separate families and orders as at present.
The use of statistical classifiers for the discrimination of
species of the genus Gyrodactylus (Monogenea)
parasitizing salmonids
Authors: SHINN A. P. , KAY J. W. , SOMMERVILLE C.
Published: July 2002

This study applies flexible statistical methods to morphometric measurements obtained via light and scanning electron
microscopy (SEM) to discriminate closely related species of Gyrodactylus parasitic on salmonids. For the first analysis,
morphometric measurements taken from the opisthaptoral hooks and bars of 5 species of gyrodactylid were derived from
images obtained by SEM and used to assess the prediction performance of 4 statistical methods (nearest neighbours; feed-forward neural network; projection pursuit regression and linear discriminant analysis). The performance of 2 methods,
nearest neighbours and a feed-forward neural network provided perfect discrimination of G. salaris from 4 other species
of Gyrodactylus when using measurements taken from only a single structure, the marginal hook. Data derived from
images using light microscopy taken from the full complement of opisthaptoral hooks and bars were also tested and nearest
neighbours and linear discriminant analysis gave perfect discrimination of G. salaris from G. derjavini Mikailov, 1975 and
G. truttae Gläser, 1974. The nearest neighbours method had the least misclassifications and was therefore assessed further
for the analysis of individual hooks. Five morphometric parameters from the marginal hook subset (total length, shaft
length, sickle length, sickle proximal width and sickle distal width) gave near perfect discrimination of G. salaris. For
perfect discrimination therefore, larger numbers of parameters are required at the light level than at the SEM level.
Development of vaccines against gastrointestinal nematodes
Authors: KNOX D. P.
Published: July 2002

Vaccination against complex metazoan parasites has become a reality with the development and registration of recombinant
protein-based vaccines against the cattle tick Boophilus microplus and the sheep cestode Taenia ovis. Progress towards the
development of similar vaccines against gastrointestinal nematodes, primarily of ruminants, is outlined within a framework
of defining the practical requirements for successful vaccination, antigen selection, recombinant protein production and
antigen delivery, be it mucosal delivery or DNA vaccination. Antigen selection strategies include the fractionation of
complex, but protective, parasite extracts, the use of antibody probes, evaluation of excretory-secretory components and
gut-expressed hidden antigens as well as antigens targeted on the basis of function such as enzyme activity. The difficulties
being encountered in recombinant protein production and their solution are discussed as are the requirements for
successful antigen delivery. Recent technological developments such as the use of functional genomics to identify new
vaccine candidates and DNA vaccination to present the selected antigen to the host immune system are discussed and are
anticipated to have a profound effect on vaccine development in the future.
Sex differences in event-related risk for major depression
Authors: MACIEJEWSKI P. K. , PRIGERSON H. G. , MAZURE C. M.
Published: July 2002

Background. This study sought to determine if women are more likely than men to experience an episode of major depression in response to stressful life events.

Method. Sex differences in event-related risk for depression were examined by means of secondary analyses employing data from the Americans' Changing Lives study. The occurrence and time of occurrence of depression onset and instances of stressful life events within a 12-month period preceding a structured interview were documented in a community-based sample of 1024 men and 1800 women. Survival analytical techniques were used to examine sex differences in risk for depression associated with generic and specific stressful life events.

Results. Women were approximately three times more likely than men to experience major depression in response to any stressful life event. Women and men did not differ in risk for depression associated with the death of a spouse or child, events affecting their relationship to a spouse/partner (divorce and marital/love problems) or events corresponding to acute financial or legal difficulties. Women were at elevated risk for depression associated with more distant interpersonal losses (death of a close friend or relative) and other types of events (change of residence, physical attack, or life-threatening illness/injury).

Conclusion. Stressful life events overall, with some exceptions among specific event types, pose a greater risk for depression among women compared to men.
Vulnerability to assaultive violence:
further specification of the sex difference in
post-traumatic stress disorder
Authors: BRESLAU N. , CHILCOAT H. D. , KESSLER R. C. , PETERSON E. L. , LUCIA V. C.
Published: July 2002

Background. We examine potential sources of the sex differences in post-traumatic stress disorder
(PTSD) in the community.

Methods. Data were obtained from a representative sample of 2181 persons aged 18–45 years in the
Detroit primary metropolitan statistical area, which is a six-county area containing more than four
million residents. A random digit dialling method was used to select the sample and a computer-assisted telephone interview was used to obtain the data. DSM-IV PTSD was assessed with respect
to a randomly selected trauma from the list of qualifying traumas reported by each respondent.

Results. The lifetime prevalence of exposure and the mean number of traumas were lower in females
than males. The overall conditional risk of PTSD (i.e. the probability of PTSD among those
exposed to a trauma) was approximately twofold higher in females than males, adjusting for the sex
difference in the distribution of trauma types. The sex difference was due primarily to females'
greater risk following assaultive violence. The sex difference in the avoidance and numbing
symptom group following assaultive violence exceeded the sex differences in other symptom groups.

Conclusions. Future research should focus on sex differences in the response to assaultive violence,
including potential explanations for females' greater probability to experience avoidance and
numbing.