bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of repeatability and phenotypic correlations in Eragrostis curvula
Authors: DI RENZO M. A. , IBAÑEZ M. A. , BONAMICO N. C. , POVERENE M. M.
Published: July 2002

Eragrostis curvula (Schrad.) Nees s. lat., a highly polymorphic polyploid complex, can be considered
as one of the most important warm season perennial grasses for the semi-arid regions of central
Argentina. In apomictically propagated and perennial plants such as weeping lovegrass, where
successive measurements can be done across time, repeatability estimates provide an indication of the
degree of influence of permanent effects on the phenotypic variation and allow prediction of future
performance from past records. Analysis of variance of the experiment showed highly significant
variation (P < 0·01) for the main factors in all four traits. Although there was very high variability
between cuts, hybrids of E. curvula exhibited considerable inter-entry variability, in particular for
those traits determining forage yield. Repeatability calculated in this experiment was highest for the
crown diameter (0·86), leaf length (0·84) and dry matter (0·84), while in panicle number (0·66) it was
lowest. Repeatability estimates for the vegetative characteristics indicate small effects of temporal
environment. The four traits studied, including panicle number with their moderate repeatability, do
not require an essentially different number of observations to obtain measures at the same level of
accuracy. For vegetative characters two harvests provided 98% of the accuracy of the total obtained
with four cuts, and for panicle number the same percentage was obtained for three harvests. This
stability of performance is a desirable characteristic for grass cultivars. Patterns of trait associations
were also described. Because leaf length is closely associated with dry matter and has high
repeatability, to use leaf length as an indirect evaluation criterion should be almost as efficient as
direct evaluation for aerial biomass yield. Reliable estimates of parameters such as repeatability and
phenotypic correlation are needed for prediction of production values and for the design of efficient
improvement programmes. For genotype evaluation additional research is required to quantify the
extent of genotype × environment interaction across years and localities of semi-arid regions.
A method for quantifying the effect of temperature treatments on plant quality
Authors: SYSOYEVA MARINA I. , KHARKINA TATJANA G.
Published: July 2002

A method that allows the effect of temperature treatments on plant quality to be quantified is
described. The proposed method is based on the analysis of temperature regions for plant quality
characteristics and enables an easier and more precise analysis of the influence of day and night
temperature on plant growth and development. Plant quality may be evaluated by the combination
of any number of plant characteristics. The proposed method can assist growers in determining what
temperature regimes are necessary to produce acceptable-quality crops on specified days.
Effects of sowing method on survival, ion uptake and
yield of wheat (Triticum aestivum L.) in sodic soils
Authors: RAJPAR I. , WRIGHT D.
Published: July 2002

Two separate experiments, in clay loam and loamy sand (prepared by mixing the clay loam with
washed sand), were performed to determine the effects of sowing method and sodicity on the survival,
ion uptake, grain yield and yield components of spring wheat (Triticum aestivum L.) cv. Kharchia-
65. Three sodicity levels (control, exchangeable sodium percentage (ESP) 5–7; low (ESP 18–20); high
(ESP 39–40)) and four sowing methods (sowing dry and pre-germinated seed and transplanting of 16
and 21-day-old seedlings) were tested. In the control and at low sodicity, sowing method had no effect
on plant survival, grain and straw dry weight per plant. However at high sodicity, these variables were
lower in plants established from pre-germinated seed than in plants established from dry seed, the
farmers' normal practice. In contrast, transplanted seedlings showed increased survival and had
significantly higher grain and straw dry weight than plants established by sowing dry seed. Differences
in grain yield between sowing method and sodicity treatments were mainly due to differences in the
number of grains per plant. Although increasing sodicity was associated with higher concentration
of Na+, and lower concentrations of K+, Ca2+, Mg2+ and
lower K+/Na+ ratio in flag leaf sap, ion concentrations were unaffected by sowing method.

It is suggested that the increased survival and yield of transplanted seedlings is due to the fact that
they are not exposed to sodicity during the sensitive stages of germination and emergence. In
addition, their already established roots and shoots may be better able to capture the resources
required to support their subsequent growth. The decreases in grain and straw dry weight per plant,
and the increases in these parameters achieved by transplanting seedlings instead of sowing dry seed,
were greater in clay loam than in loamy sand. Further studies are required to determine whether the
responses to transplanting observed here also occur in sodic soils under field conditions, and to
investigate the technical and economic feasibility of adopting this technique in commercial
agriculture.
Effect of potassium fertilizer on the yield, quality and
potassium offtake of sugar beet crops grown on soils of
different potassium status
Authors: MILFORD G. F. J. , ARMSTRONG M. J. , JARVIS P. J. , HOUGHTON B. J. , BELLETT-TRAVERS D. M. , JONES J. , LEIGH R. A.
Published: July 2002

The effect of different rates of potassium (K) fertilizer on the yield and quality of sugar beet was
studied in a series of 26 trials on soils of different type and K index between 1992 and 1997. There
were few yield responses even though the majority of trials were on soils of low K index, and large
quantities of fertilizer were applied (0–600 kg K/ha). Potassium offtakes (kg/ha) in the harvested beet
increased asymptotically, not linearly, with yield and were much larger for a given yield on high K
index soils than on low index soils. Commercially acceptable concentrations of beet K for processing
are in the range 700 to 1000 mg K/100 g sugar. Concentrations in excess of this decrease the amount
of sugar crystallized from the extracted juice. They were not greatly affected by large applications of
fertilizer K but were strongly influenced by long-established differences in soil exchangeable K (Kex)
due to soil type, previous cropping or manuring history.

The asymptotic nature of the K offtake[ratio ]yield relationship was confirmed by factory tarehouse
measurements relating to the national sugar beet crop delivered during the 1993–97 UK processing
campaigns. Potassium offtakes generally increased linearly with yield up to 60–70 adjusted t of clean
beet/ha, but increased little beyond that. The amount of K removed by a 60–70 t/ha crop of beet
varied from 70 kg K/ha on low K index sandy loams to 120 kg K/ha on clay soils of K index 3 and
above. Further increases in yield decreased the amount of K in fresh beet from 1·7 to 1·4 kg K/t on
low K index soils, and from 3·6 to 2·5 kg K/t on high K index soils.

An analysis of data from individual fields of commercially grown sugar beet showed that much of
the site and season variation in the K content of beet was due to differences in K uptake driven by
Kex, and to differential effects of nitrogen (N) supply on K uptake and sugar yield. Regressions on
Kex and total crop N (kg/ha) accounted for c. 30 and 50% of the variance in beet K content,
respectively, and the two together for over 60%. Total N uptake by the crops ranged from 100 to
550 kg N/ha. The total K content of the crop and the amounts of K in the beet (kg/ha) both
increased linearly with crop N over the whole of this range, whereas sugar yield increased
asymptotically with total uptakes of N up to 250–300 kg N/ha. Consequently, low yielding crops
grown on soils in which N and K were freely available produced beet of poor K quality. However,
the asymptotic relationship between beet K (kg/ha) and yield implies that, in many situations, the
processing quality of the beet could be improved by increasing yield through better agronomy.
Long-term yield patterns in barley-based cropping systems in Northern Syria. 2. The role of feed legumes
Authors: JONES M. J. , SINGH M.
Published: July 2002

Rotations of barley with feed legumes produce more biomass and crude protein than barley-fallow
and continuous barley sequences, but scope remains to improve the potential value to farmers of feed
legume-based systems. This paper summarizes 6-year results from two sites from 2-year rotations of
barley with: narbon vetch (Vicia narbonensis) and lathyrus (Lathyrus sativus), each harvested mature;
and common vetch (Vicia sativa), harvested by simulated green-grazing and mature, all in factorial
combination with four NP fertilizer regimes applied biennially to the barley.

Mean yield differences between rotations were quite small, but at the drier site the narbon vetch
rotation was significantly superior in both total biomass and crop total nitrogen. Other results
implied yield compensation between barley and legume phases: barley performance was relatively
depressed at the wetter site after high-yielding narbon vetch but was relatively enhanced at both sites
after green-grazed common vetch. Evidence from year-round soil-water monitoring suggests that the
benefit following green grazing may have arisen, in part, from a small carry-over of profile moisture
between crops not much inferior to that residual from a fallow year. Both crop phases responded
strongly to biennial P fertilizer; and barley responded strongly to three rates of N-fertilizer, but a
sometimes significant curvilinear component to this response reflected a tendency for grain yields to
be depressed by added nitrogen in the driest years. But interactions between N-rates and rotations
were not significant.

It was concluded that narbon vetch may have greater potential than common vetch and lathyrus
for mature harvest in drier areas, but its unsuitability for grazing green is a limitation. Flexibility of
utilization is important, to accommodate the needs of different farmers and the exigencies of different
seasons. The green-graze option has major potential where there is a demand for high-quality spring
grazing; and indications that barley may be as productive after green-grazed vetch as after a year of
fallow suggest an alternative approach for farmers who have previously avoided legumes in order to
maximize barley production.
ANALYSIS OF POSTPARTUM LACTATIONAL AMENORRHOEA IN RELATION TO BREAST-FEEDING: SOME METHODOLOGICAL AND PRACTICAL ASPECTS
Authors: LE STRAT Y. , THALABARD J. C.
Published: July 2002

A large multicentre epidemiological study was carried out by WHO between 1991 and 1995 to analyse the duration of lactational amenorrhoea in relation to breast-feeding. The main results of this analysis, which used classical statistical modelling, have been already published. However, some specific aspects of the postpartum fertility amenorrhoea and breast-feeding covariates, and more specifically the observed progressive exhaustion of the breast-feeding inhibitory effect on the reproductive axis, may justify a closer look at the validity of the statistical tools. Indeed, as has already been emphasized, analysis of large longitudinal data sets in reproduction often faces three difficulties: (i) the precise determination of the event of interest, (ii) the way to handle the time evolution of both the studied variables and their effect on the event of interest and (iii) the often discrete nature of the data and the associated problem of tied events. The first objective of the present work was to give additional insights into the estimation and quantification of the dynamics of the effect of breast-feeding over time, considering this covariate either as fixed or time-dependent. The second objective was to show how to perform the analyses using corresponding adapted procedures in widely available statistical packages, without the need for acquiring particular programming skills.
ISRAELI MILITARY IQ TESTS: GENDER DIFFERENCES SMALL; IQ GAINS LARGE
Authors: FLYNN JAMES R.
Published: July 2002

From 1971 to 1984, the Israeli Defence Forces administered two tests unaltered that qualify as IQ tests. These were the Matrices and the Instructions tests. The former is an adaptation of Raven's Progressive Matrices, similar to the original in that there are clusters with progressive difficulty and an escalation of difficulty throughout the test. The raw score range is from 4 to 35. The Instructions test is adapted from the old US Army Alpha Instructions Test and is described as an Otis-type verbal test. It includes 21 open-ended instructions. Typical items: write the last letter of the word which is the opposite of black; write the third letter of the largest word among the following four words; find the word beginning and ending with the same letter and write that letter. There are similar questions using numbers rather than letters. Both tests are timed, and most subjects do not complete either. There is no penalty for wrong answers (Col. Moshe Even-Chen, personal communication, 14 March 1990; Gal, 1986, pp. 79 and 95; Judy Goldenberg, personal communications, 4 March 1991 and 25 April 1993).
Comparison of heat and pressure treatments of skim milk,
fortified with whey protein concentrate, for set yogurt preparation:
effects on milk proteins and gel structure
Authors: NEEDS ERIC C. , CAPELLAS MARTA , BLAND A. PATRICIA , MANOJ PRETIMA , MACDOUGAL DOUGLAS , PAUL GOPAL
Published: July 2002

Heat (85 °C for 20 min) and pressure (600 MPa for 15 min) treatments
were applied to skim milk fortified by addition of whey protein concentrate. Both
treatments caused > 90% denaturation of β-lactoglobulin. During heat treatment
this denaturation took place in the presence of intact casein micelles; during pressure
treatment it occurred while the micelles were in a highly dissociated state. As a result
micelle structure and the distribution of β-lactoglobulin were different in the two
milks. Electron microscopy and immunolabelling techniques were used to examine
the milks after processing and during their transition to yogurt gels. The disruption
of micelles by high pressure caused a significant change in the appearance of the milk
which was quantified by measurement of the colour values L*, a* and b*. Heat
treatment also affected these characteristics. Casein micelles are dynamic structures,
influenced by changes to their environment. This was clearly demonstrated by the
transition from the clusters of small irregularly shaped micelle fragments present in
cold pressure-treated milk to round, separate and compact micelles formed on
warming the milk to 43 °C. The effect of this transition was observed as significant
changes in the colour indicators. During yogurt gel formation, further changes in
micelle structure, occurring in both pressure and heat-treated samples, resulted in a
convergence of colour values. However, the microstructure of the gels and their
rheological properties were very different. Pressure-treated milk yogurt had a much
higher storage modulus but yielded more readily to large deformation than the
heated milk yogurt. These changes in micelle structure during processing and yogurt
preparation are discussed in terms of a recently published micelle model.
Method for the selection of Lactococcus lactis mutants producing excess carbon dioxide
Authors: EL ATTAR AISHA , MONNET CHRISTOPHE , AYMES FRÉDÉRIC , CORRIEU GEORGES
Published: July 2002

One of the characteristics of Roquefort cheese is the presence of irregularly
shaped openings. Although many factors affect the development of opening in blue-veined
cheeses (Martley & Crow, 1996), the limiting step in the case of Roquefort
cheese is the production of CO2 by lactic acid bacteria (J.-P. Reverbel, pers. comm.).
Most of the opening occurs after moulding; the process is difficult to control and
many manufacturing runs result in cheeses with an insufficient opening. Concentrated
suspensions of Leuconostoc strains are used to increase the production of CO2
(Devoyod & Muller, 1969), but it would clearly be useful to have microorganisms that
produce larger quantities of the gas. McKay & Baldwin (1974) isolated a spontaneous
mutant of Lactococcus lactis that produced more acetoin and CO2 than the parent
strain. This mutant was lactate dehydrogenase (LDH)-deficient, which favoured the
conversion of pyruvate into end products other than lactate. Following nitrosoguanidine
mutagenesis, we isolated three Lc. lactis mutants whose LDH activities
were reduced to varying extents and which produced varying amounts of CO2
(Boumerdassi et al. 1997). Subsequent work showed that these mutants were
unstable on successive subculture in milk or synthetic broth (El Attar et al. 2000).

The aim of our current work was to select a large number of Lc. lactis mutants
producing excess CO2. This would increase the probability of selecting stable
mutants and also provide a collection of strains with differing gas production
activities. Currently available screening methods are, however, unsuitable for
processing large numbers of mutants, which is why we have developed an improved
screening method.
Non-covalent binding of benzaldehyde to β-lactoglobulin: characterisation by spectrofluorimetry and electrospray ionisation mass-spectrometry
Authors: RELKIN PERLA , MOLLE DANIEL , MARIN ISABELLE
Published: July 2002

β-Lactoglobulin (β-lg), which is found in the milk of several mammal species, is
the most abundant protein in bovine whey (McKenzie, 1971). The interaction
properties of β-lg with a large variety of small hydrophobic ligands have been
extensively studied (Sawyer et al. 1998). β-Lg belongs to the super-family of
hydrophobic molecule transporters called the lipocalins, which characteristically
bind hydrophobic ligands inside a central calyx (Godovac-Zimmermann, 1988; Perez
et al. 1989; Brownlow et al. 1997; Wu et al. 1997; Qin et al. 1998).

At present, whey protein concentrates containing a high percentage of β-lg are
commercially available in a very large quantity, but most of the processes used in
milk technology involve heat-treatments that are known to affect the initial
conformational state of β-lg. Such conformational changes have consequences for
both the physicochemical and functional properties in food systems, including a
decrease in the availability of lysine, due to Maillard reactions (Léonil et al. 1997) and
a decrease in the affinity constant for binding to retinol (Laligant et al. 1991) and to
flavour compounds (O'Neil & Kinsella, 1988). In the field of protein-volatile
compound interactions, we have recently reported a significant enhancement of
foaming properties of β-lg solutions (50 mM-NaCl, pH 6) in the presence of aroma
compounds such as isoamyl acetate (Marin & Relkin, 1999), benzaldehyde (BZA;
Marin & Relkin, 2000) and vanillin (Relkin & Vermersh, 2000). The observed increase
in foaming properties of β-lg was postulated to be due to formation of surface active
complexes between β-lg and aroma compounds.

In the present work we have investigated the interaction between a β-lg
concentrate (prepared by ultra-diafiltration on an industrial scale) and BZA;
particularly, evidence was sought for the presence of covalently bound monomers,
dimers and lactolated monomers.
Effect of added salt and increase in ionic strength on skim milk electroacidification performances
Authors: BAZINET LAURENT , IPPERSIEL DENIS , GENDRON CHRISTINE , MAHDAVI BEHZAD , AMIOT JEAN , LAMARCHE FRANÇOIS
Published: July 2002

Bipolar-membrane electroacidification (BMEA) technology, which uses the property of bipolar membranes to split water and the demineralization action of cation-exchange membranes (CEM), was tested for the production of acid casein. BMEA has numerous advantages in comparison with conventional isoelectric precipitation processes of proteins used in the dairy industry. BMEA uses electricity to generate the desired ionic species to acidify the treated solutions. The process can be precisely controlled, as electro-acidification rate is regulated by the effective current density in the cell. Water dissociation at the bipolar membrane interface is continuous and avoids local excess of acid. In-situ generation of dangerous chemicals (acids and bases) reduces the risks associated with the handling, transportation, use and elimination of these products. The aim of this study was to evaluate the performance of BMEA in different conditions of added ionic strength (μadded = 0, 0·25, 0·5 and 1·0 M) and added salt (CaCl2, NaCl and KCl).The combination of KCl and μadded = 0·5 M gave the best results with a 45% decrease in energy consumption. The increased energy efficiency was the result of a decrease in the anode/cathode voltage difference. This was due to an increase of conductivity, produced by addition of salt, necessary to compensate for the lack of sufficiently mobile ions in the skim milk. However, the addition of salts, irrespective of type or ionic strength, increased the required operation time. The protein profile of isolates were similar under all experimental conditions, except at 1·0 M-CaCl2.
Comparison of cell surface proteinase activities within the
Lactobacillus genus
Authors: GILBERT CHRISTOPHE , BLANC BRIGITTE , FROT-COUTAZ JACQUES , PORTALIER RAYMOND , ATLAN DANIÈLE
Published: July 2002

Whole cells of Lactobacillus delbrueckii subsp.
bulgaricus CNRZ 397 (Lb.
bulgaricus CNRZ 397) are able to hydrolyse α- and β-caseins.

We have isolated a
mutant of Lb. bulgaricus altered for growth in milk and unable
to
hydrolyse α- or β-casein. Normal growth was restored by adding
amino
acids or tryptone to milk. No
significant difference between the peptidase activities of parent and mutant
strains
was observed. The cell surface caseinolytic activities of three lactobacilli

species and
Lactococcus lactis subsp. lactis (Lc. lactis)

were compared. As expected, the
characteristics of the cell surface proteinase activity of
Lb. casei were similar to those
of Lc. lactis. We showed that the cleavage specificities of
the cell surface proteinase
activities from lactobacilli were species-dependent and at least three

types of activity
were distinguished. The regulation of the biosynthesis of cell surface
proteinase
activities was medium-dependent and different within the
Lactobacillus genus and
even within the Lb. delbrueckii species. In contrast to
Lb. bulgaricus, the cell surface
proteinase activity of Lb. lactis was totally inhibited in a
medium rich in peptides or
amino acids. In contrast, the cell surface of Lb. helveticus
probably displayed two
proteinases with different cleavage specificities and with a biosynthesis
regulation
sensitive to different medium components.
Antitumour activity of yogurt: study of
possible immune mechanisms
Authors: PERDIGÓN GABRIELA , VALDEZ JUAN CARLOS , RACHID MIRTA
Published: July 2002

The effect of yogurt on the inhibition of colon
tumours induced by 1,2-dimethylhydrazine in BALB/c mice
has been studied, and the hypothesis examined
that yogurt induces a great reduction in the inflammatory
immune response and
inhibits tumour growth. Mice were assigned to five
experimental groups: a control
group fed with a conventional balanced diet, and four
other test groups that received
yogurt supplements for 2, 5, 7 or 10 consecutive days. At
the end of each feeding
period, mice were given subcutaneous injections of
1,2-dimethylhydrazine (20 mg/kg) once a week for 8 weeks.
After tumour induction,
yogurt was given again for 2,
5, 7 or 10 consecutive days each 10 d for 20 weeks. By
week 20, 70% of the animals
in the control group had developed colorectal tumours.
From week 8, there was a
considerable infiltration of mononuclear cells into
the lamina propria of the large
intestine. There was an increase in the number of
IgG-producing cells and a slight
increase in the IgA-secreting cells, and of CD8+
but not CD4+ T lymphocytes, a high
level of β-glucuronidase activity in the intestinal
fluid and leucocytosis with
neutrophilia in the blood. However, in the test groups
given yogurt tumour growth
was inhibited, the effect being more evident with 7 or
10 d treatment. The
inflammatory immune response as measured by the
characteristics we assessed was
also reduced, with an increase in the IgA-secreting cells
and in CD4+ T lymphocytes.
The blood count was similar to that of normal animals and
no colorectal tumours
were observed in week 20. We suggest that one of the
mechanisms by which yogurt
exerts antitumour activity is through its immunomodulator
activity, by reducing
the inflammatory immune response, which was markedly
increased when the carcinogen was administered.
Proteolytic activity of lactococcal strains from
water-buffalo Mozzarella starter cultures
Authors: MAURIELLO GIANLUIGI , MOSCHETTI GIANCARLO , BLAIOTTA GIUSEPPE , VILLANI FRANCESCO , COPPOLA SALVATORE
Published: July 2002

Growth and proteolytic activity of Lactococcus
lactis strains were
investigated in milks subjected to different heat treatments.
Only 13·7% of the
strains were of proteolytic phenotype. Proteinase-positive
(Prt+) strains exhibited a
proteolytic activity that increased when the level of heat
treatment was reduced and
grew to a higher level than proteinase-negative
(Prt−) strains in low-heat-treated
milk. When grown in autoclaved reconstituted skim milk, both
Prt− and Prt+ strains
had the same specific growth rate. Total DNA from four
Prt+ and eleven Prt− strains
was extracted and used for polymerase chain reaction
amplification of fragments
belonging to genes encoding for cell wall proteinase.
Specific amplification products
were displayed by all the Prt+
strains, and by the Prt−
strain Lc. lactis subsp. lactis
NWC 125. Reverse transcriptase-polymerase chain reaction
was performed to detect the transcript of the proteinase genes.
In addition to the Prt+ strains, the experiment
also detected the specific transcript in Lc.
lactis subsp. lactis NWC 125, suggesting
that other structural or functional deficiencies
occurred in this strain.
Effects of calcium soaps and rumen undegradable protein on the
milk production and composition of dairy ewes
Authors: CASALS RAMON , CAJA GERARDO , SUCH XAVIER , TORRE CELINA , CALSAMIGLIA SERGIO
Published: July 2002

Forty-eight Manchega dairy ewes were used during a complete lactation
in a 2×2 factorial design to determine the effects of supplementing diets with fat
(calcium soaps of palm oil fatty acids, CSFA) and rumen undegradable protein
(RUP) on milk production and composition. Factors tested were amounts of CSFA
(0 or 200 g/kg) and RUP (300 or 450 g/kg crude protein) in the concentrate. RUP
was altered by adding a mixture of maize gluten meal and blood meal. Lactation was
divided into one nursing period (period 1, weeks 1–4), and three milking periods
(periods 2–4, weeks 5–8, 9–14 and 15–21). Concentrates were given at 0–8 kg/d during
periods 1 and 2, and at 0–6 kg/d in periods 3 and 4. Ewes grazed rotationally in an
Italian rye-grass pasture and received a daily supplement of 0·8 kg vetch–oat hay
during period 1, and 0·3 kg lucerne hay during periods 2–4. For the whole lactation,
supplemental fat markedly increased milk fat content (+23%) and yield (+16%),
and decreased milk protein content (−9%). The positive effect of feeding CSFA on
milk fat content was more evident at the beginning of lactation; however, its
negative effect on milk protein was more pronounced in late lactation. Supplementary
RUP had little effect, increasing milk protein content only in period 3,
when the crude protein content of pasture was lower. Milk yield and lamb growth
were not affected by dietary treatments. The results indicated that CSFA can be
useful for increasing the milk fat content of dairy ewes at pasture, which may help
farmers to produce milk reaching the minimum requirements of fat content for the
cheese industry.
Bovine immunoglobulin G, β-lactoglobulin, α-lactalbumin and serum
albumin in colostrum and milk during the early post partum period
Authors: LEVIEUX DIDIER , OLLIER ALAIN
Published: July 2002

Colostrum and milk samples from 60 Holstein–Friesian cows were
analysed for concentrations and yields of immunoglobulin G (IgG), β-lactoglobulin
(β-lg), α-lactalbumin (α-la) and serum albumin (BSA) throughout the first 16
milkings post partum (8 d of lactation) using a single radial immunodiffusion assay.
Concentrations (mg/ml, means±SD) at first
milking were IgG 59·8±28·5, β-lg
14·3±4·6, α-la 2·04±0·6, BSA 1·21±0·44. Large variations were recorded for IgG
concentrations (15·3–176·2 mg/ml) and yields (0·2–925 g). Cows in their first lactation produced significantly lower concentrations and yields of colostral IgG than cows in later lactations. A colostral yield of IgG below the 100 g required to prevent calf hypo-γ-globulinaemia was found in 18·3% of the cows. The concentrations of IgG, β-lg and BSA dropped abruptly in subsequent milkings and α-la concentration
decreased slowly. The mean IgG concentration was <2 mg/ml after eight milkings and <1 mg/ml after fifteen milkings. However, IgG concentration did not differ significantly, at the 1% level, during milkings 11–15. The results were tabulated to make it possible to calculate the excess of whey proteins that would be obtained if early milks were illegally added to the milk supply.
Convectively driven exchange flow in a stratified sill-enclosed basin
Authors: FINNIGAN T. D. , IVEY G. N.
Published: July 2002

Laboratory experiments are used to investigate the processes governing steady convectively
driven circulation in a basin that communicates with a large external reservoir
over a shallow sill. The motion is maintained by a steady loss of buoyancy distributed
over the surface of the basin. Turbulent convection associated with the forcing produces
a horizontal buoyancy gradient across the sill and the resulting mean flow
consists of a layer directed into the basin near the surface with a dense counter flow
below.

To first order, the magnitude of the exchange flow over the sill is determined by
the horizontal momentum balance within the basin. Measurements of the mean and
turbulent flow fields are used to show that inertia, buoyancy and friction may each
contribute significantly to the balance. The interior flow produces a horizontal pressure
gradient near the surface which must also contribute to the momentum balance. The
density of the lower layer at the sill reflects the cumulative effect of interior processes,
such as mixing, and these in turn influence the hydraulically controlled exchange
flow over the sill. The basin dynamics are therefore coupled in a nonlinear fashion
with the submaximal sill exchange. This coupling is investigated first by showing how
interior processes are affected by changes in the magnitude of the forcing, and then
by observing the associated variation of the flow state at the sill. The flow state is
defined in terms of its relative proximity to the theoretical maximal exchange limit.
Results show that the exchange flows are submaximal with flow rate approximately
85% of the maximal limit. This state appears to change very little in response to
increasing forcing.

For a stratified basin, which exhibits a deep stagnant layer under the convectively
driven near-surface exchange flow, the possibility of basin ventilation or erosion
of deep fluid exists in the long term. This process and its dependence on external
parameters is also explored.
The viscosity of a dilute suspension of rough spheres
Authors: WILSON HELEN J. , DAVIS ROBERT H.
Published: July 2002

We consider the flow of a dilute suspension of equisized solid spheres in a viscous
fluid. The viscosity of such a suspension is dependent on the volume fraction, c, of
solid particles. If the particles are perfectly smooth, then solid spheres will not come
into contact, because lubrication forces resist their approach. In this paper, however,
we consider particles with microscopic surface asperities such that they are able to
make contact. For straining motions we calculate the O(c2) coefficient of the resultant
viscosity, due to pairwise interactions. For shearing motions (for which the viscosity
is undetermined because of closed orbits on which the probability distribution is
unknown) we calculate the c2 contribution to the normal stresses
N1 and N2. The
viscosity in strain is shown to be slightly lower than that for perfectly smooth spheres,
though the increase in the O(c) term caused by the increased effective radius due to
surface asperities will counteract this decrease. The viscosity decreases with increasing
contact friction coefficient. The normal stresses N1 and N2 are zero if the surface
roughness height is less than a critical value of 2.11 × 10−4 times the particle radius,
and then become negative as the roughness height is increased above this value. N1
is larger in magnitude than N2.
Convection in a horizontally heated sphere
Authors: McBAIN G. D.
Published: July 2002

Natural convection in horizontally heated spherical fluid-filled cavities is considered in
the low Grashof number limit. The equations governing the asymptotic expansion are
derived for all orders. At each order a Stokes problem must be solved for the momentum
correction. The general solution of the Stokes problem in a sphere with arbitrary
smooth body force is derived and used to obtain the zeroth-order (creeping) flow and
the first-order corrections due to inertia and buoyancy. The solutions illustrate the two
mechanisms adduced by Mallinson & de Vahl Davis (1973, 1977) for spanwise flow in
horizontally heated cuboids. Further, the analytical derivations and expressions clarify
these mechanisms and the conditions under which they do not operate. The inertia
and buoyancy effects vanish with the Grashof and Rayleigh numbers, respectively,
and both vanish if the flow is purely vertical, as in a very tall and narrow cuboid.
The formation and evolution of a diffusive interface
Authors: MOLEMAKER M. JEROEN , DIJKSTRA HENK A.
Published: July 2002

The formation and evolution of a diffusive interface in a
stable salt-stratified layer cooled from above is studied in a
two-dimensional geometry by direct numerical simulation. For a typical
example with realistic parameters, the evolution of the flow is computed
up to the moment where three layers can be distinguished. Focus is on
the development of the first mixed layer. The convective velocity
scaling as proposed by Hunt (1984) and previously proposed expressions
for the interfacial heat flux (Huppert 1971; Fernando 1989a)
are shown to correspond well with the results of the simulation. The
evolution of the first layer can be well described by an entrainment
relation based on a local balance between kinetic and potential energy
with mixing efficiency γ. The new entrainment relation is shown
to fit the numerical results well and an interpretation of γ in
terms of the overall energy balances of the flow is given.

Previously, two rival mechanisms have been proposed that determine
the final thickness of the first layer (Turner 1968; Fernando 1987).
One of the distinguishing features of both mechanisms is whether a
transition in entrainment regime – as the first layer develops
– is a necessary condition for the mixed layer to stop growing.
Another is the presence of a buoyancy jump over the interface before
substantial convection in the second layer occurs. From the numerical
results, we find a significant buoyancy jump even before the thermal
boundary layer ahead of the first layer becomes unstable. Moreover, the
convective activity in the second layer is too small to be able to stop
the growth of the first layer. We therefore favour the view proposed by
Fernando (1987) that a transition in entrainment regime determines the
thickness of the first layer. Following this, a new one-dimensional
model of layer formation is proposed. Important expressions within this
model are verified using the results of the numerical simulation. The
model contains two constants which are determined from the numerical
results. The results of the new model fit experimental results quite
well and the parameter dependence of the thickness of the first layer
is not sensitive to the values of the two constants.
Nonlinear evolution and secondary instabilities
of Marangoni convection in a liquid–gas system
with deformable interface
Authors: GOLOVIN A. A. , NEPOMNYASHCHY A. A. , PISMEN L. M.
Published: July 2002

The paper presents a theory of nonlinear evolution and
secondary instabilities in
Marangoni (surface-tension-driven) convection in a two-layer
liquid–gas system with
a deformable interface, heated from below. The theory takes into account the motion
and convective heat transfer both in the liquid and in the gas layers. A system of
nonlinear evolution equations is derived that describes a general case of slow
long-scale evolution of a short-scale hexagonal Marangoni convection pattern near the
onset of convection, coupled with a long-scale deformational Marangoni instability.
Two cases are considered: (i) when interfacial deformations are negligible; and (ii)
when they lead to a specific secondary instability of the hexagonal convection.

In case (i), the extent of the subcritical region of the hexagonal Marangoni
convection, the type of the hexagonal convection cells, selection of
convection patterns – hexagons, rolls and squares – and
transitions between them are studied, and the
effect of convection in the gas phase is also investigated.
Theoretical predictions are compared with experimental observations.

In case (ii), the interaction between the short-scale hexagonal
convection and the
long-scale deformational instability, when both modes of Marangoni convection are
excited, is studied. It is shown that the short-scale convection
suppresses the deformational instability. The latter can appear as a
secondary long-scale instability of
the short-scale hexagonal convection pattern. This secondary instability is shown to
be either monotonic or oscillatory, the latter leading to the excitation of
deformational waves, propagating along the short-scale hexagonal
convection pattern and modulating its amplitude.
Axisymmetric motion of capsules through
cylindrical channels
Authors: QUÉGUINER CHRISTOPHE , BARTHÈS-BIESEL DOMINIQUE
Published: July 2002

A boundary integral method is used to model the flow of capsules
into pores. An
axisymmetric configuration is considered where the capsule and
the pore axis coincide.
The channel is a cylinder with hyperbolic entrance and exit regions.
The capsule has a
discoidal unstressed shape, is filled with a Newtonian liquid
and is enclosed by a very
thin membrane with various elastic properties (neo-Hookean or area-incompressible).
The motion of the internal capsule liquid and of the suspending fluid is
governed by
the Stokes equations whose solution is expressed as boundary integrals.
Those are
computed by a collocation technique, where points are distributed on the
capsule
interface, on the channel walls and on the entrance and exit sections of
the flow
domain. The capsule interface mechanics follow the theory of large deformations
of
elastic membranes. The numerical model uses a forward time-stepping method,
where
the position and the deformation of the capsule are computed at each time
step.

The model allows the study of the effect of a number of parameters (capsule
size
and geometry, membrane elastic properties) on the flow. The entrance length
in the
pore, the steady additional pressure drop at equilibrium and the capsule
deformed
profiles are determined. It is found that the entrance of a capsule
into a pore is not
sensitive to downstream conditions; but the length of tube necessary to
reach steady
conditions depends strongly on capsule size and membrane behaviour. Bursting
of
capsules with a neo-Hookean membrane is predicted to occur through a phenomenon
of continuous elongation. The flow of a capsule with a membrane that resists
area
dilatation depends strongly on particle size and shape.
Accelerated scalar dissipation in a vortex
Authors: FLOHR P. , VASSILICOS J. C.
Published: July 2002

A scalar patch forms spiral structure when it wraps around
an isolated vortex. It is
shown that this wind-up process leads to accelerated diffusion during a
time range
TS<t<TD.
The lower limit TS is the time needed to
create a well-defined spiral, and
the upper limit TD is the diffusive
time scale of the scalar field θ in the vortex. Whereas the scaling
TD∼Pe1/3
is independent of the particular spiral topology, the accelerated
decay of the scalar variance θ2[bar](t)
for
earlier times is directly linked to the space-filling
property of the spiral and is found to scale as
θ2[bar](0)−θ2[bar](t)∼
(Pe1/3t)
3(1−D′K).
D′K is the Kolmogorov capacity of the
spiral; it is defined in the range
1/2<D′K<1 and it is the most
suitable measure of the spiral's space-filling property.
Stokes flow in collapsible tubes: computation and experiment
Authors: HEIL MATTHIAS
Published: July 2002

This paper is concerned with the problem of viscous flow in

an elastic tube. Elastic

tubes collapse (buckle non-axisymmetrically) when the transmural pressure
(internal

minus external pressure) falls below a critical value. The tube's

large deformation during the buckling leads to a strong interaction between

the fluid and solid mechanics.

In this study, the steady three-dimensional Stokes equations are used
to analyse

the slow viscous flow in such a tube whose deformation is described by
geometrically

nonlinear shell theory. Finite element methods are used to solve

the large-displacement

fluid–structure interaction problem. Typical wall deformations and

flow fields in the

strongly collapsed tube are shown. Extensive parameter studies illustrate

the tube's flow characteristics (e.g. volume flux as a function of
the applied

pressure drop through

the tube) for boundary conditions corresponding to the four fundamental
experimental

setups. It is shown that lubrication theory provides an excellent approximation
of

the fluid traction while being computationally much less expensive than
the solution

of the full Stokes equations. Finally, the computational predictions for
the flow

characteristics and the wall deformation are compared to the results obtained
from

an experiment.
Tandem submerged cylinders each subject to zero drag
Authors: TUCK E. O. , SCULLEN D. C.
Published: July 2002

Two identical circular cylinders are submerged to the same depth
in tandem in a
stream. There are separation distances between the cylinder centres such
that the
combination makes no downstream waves, and hence is subject to zero net
wave
drag. In general there is then a non-zero equal and opposite horizontal
force on each
cylinder. However, there are special depths of submergence such that this
interaction
force between the cylinders also vanishes, and hence each cylinder is separately
free
of horizontal force. The parameter range for this phenomenon is explored
both
by linear theory for cylinders of small radius, and by a fully nonlinear
computer
program. For example, a configuration with a separation distance of approximately

one half-wavelength gives zero force on each cylinder when the depth of
submergence
is approximately three-quarters of the separation distance.
The motion of an intense vortex near topography
Authors: McDONALD N. ROBB
Published: July 2002

The initial value problem for the motion of an intense, quasi-geostrophic,

equivalent-barotropic, singular vortex near an infinitely long escarpment
is studied in three
parts. First, for times small compared to the topographic wave timescale
the motion
of the vortex is analysed by deriving an expression for the secondary circulation

caused by the advection of fluid columns across the escarpment. The secondary

circulation, in turn, advects the primary vortex and integral expressions
are found
for its velocity components. Analytical expressions in terms of integrals
are found
for the vortex drift velocity components. It is found that, initially,
cyclones propagate
away from the deep water region and anticyclones propagate away from the
shallow
water region. Asymptotic evaluation of the integrals shows that both cyclones
and
anticyclones eventually propagate parallel to the escarpment with shallow
water on
their right at a steady speed which decays exponentially with distance
from the
escarpment. Secondly, it is shown that for times comparable to, and larger
than, the
wave timescale, the vortex always resonates with the topographic wave field.
The flux
of energy in the topographic waves leads to a loss of energy in the vortex
and global
energy and momentum arguments are used to derive an equation for the distance
(or,
equivalently, the vortex velocity) of the vortex from the escarpment. It
is shown that
cyclones, provided they are initially within an O(1) distance

(here a unit of distance is
dimensionally equivalent to one Rossby radius of deformation) from the
escarpment,
drift further away from the deep water (i.e. toward higher ambient potential
vorticity),
possibly crossing the escarpment and accumulate at a distance of ≈1.2
on the shallow
side of the escarpment. For distances larger than 1.2 there is essentially
no drift of
the vortex perpendicular to the escarpment. Anticyclones display similar
behaviour
except they drift in the opposite direction, i.e. away from the shallow
water or toward
lower ambient potential vorticity. Third, the method of contour dynamics
is used to
describe the evolution of the vortex and the interface representing the
initial potential
vorticity jump between the shallow and deep water regions. The contour
dynamic
results are in good quantitative agreement with the analytical results.
Helical vortices in swirl flow
Authors: ALEKSEENKO S. V. , KUIBIN P. A. , OKULOV V. L. , SHTORK S. I.
Published: July 2002

Helical vortices in swirl flow are studied theoretically and experimentally.

A theory of helical vortices has been developed. It includes the following
results:
an analytical solution describing an elementary helical vortex structure
– an infinitely
thin filament; a solution for axisymmetrical vortices accounting for the
helical shape
of vortex lines and different laws of vorticity distribution; a formula
for calculation
of the self-induced velocity of helical vortex rotation (precession) in
a cylindrical
tube; an explanation of the zone with reverse flow (recirculation zone)
arising in swirl
flows; and the classification of vortex structures.

The experimental study of helical vortices was carried out in a vertical
hydrodynamical
vortex chamber with a tangential supply of liquid through turning nozzles.

Various vortex structures were formed owing to changing boundary conditions
on the
bottom and at the exit section of the chamber. The hypothesis of helical
symmetry
is confirmed for various types of swirl flow. The stationary helical vortex
structures
are described (most of them for the first time) the features of which agree
with the
results and predictions of the theoretical model developed. They are the
following:
a rectilinear vortex; a composite columnar vortex; helical vortices screwed
on the
right or on the left; a vortex with changing helical symmetry; a double
helix – two
entangled vortex filaments of the same sign.
Secondary instabilities in rapidly rotating fluids:
inertial wave breakdown
Authors: KERSWELL R. R.
Published: July 2002

Inertial waves are a ubiquitous feature of rapidly rotating fluids.
Although much is
known about their initial excitation, little is understood about their
stability. Experiments
indicate that they are generically unstable and in many cases catastrophically

so, quickly causing the whole flow to collapse to small-scale disorder.
The linear
stability of two three-dimensional inertial waves observed to break down
in the
laboratory is considered here at experimentally small but finite Ekman
numbers of
[les ]10−4. Surprisingly small threshold amplitudes for
instability are
found. The results support the conjecture that triad resonances are the
generic
mechanism for secondary instability in rapidly rotating fluids but also
highlight the
ability of geostrophic flows to derive energy through a finite-amplitude
inertial wave.
This latter finding may go some way to explaining the significant mean
circulations
typically observed in inertial wave experiments.