bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrodynamic interactions and collision
efficiencies of spherical drops covered with an
incompressible surfactant film
Authors: BLAWZDZIEWICZ J. , WAJNRYB E. , LOEWENBERG MICHAEL
Published: July 2002

A theory is developed for the hydrodynamic interactions of surfactant-covered
spherical drops in creeping flows. The surfactant is insoluble, and flow-induced
changes of surfactant concentration are small, i.e. the film of adsorbed surfactant is
incompressible.

For a single surfactant-covered drop in an arbitrary incident flow, the Stokes
equations are solved using a decomposition of the flow into surface-solenoidal
and surface-irrotational components on concentric spherical surfaces. The surface-solenoidal component is unaffected by surfactant; the surface-irrotational component
satisfies a slip-stick boundary condition with slip proportional to the surfactant
diffusivity. Pair hydrodynamic interactions of surfactant-covered bubbles are computed
from the one-particle solution using a multiple-scattering expansion. Two terms in a
lubrication expansion are derived for axisymmetric near-contact motion.

The pair mobility functions are used to compute collision efficiencies for equal-size
surfactant-covered bubbles in linear flows and in Brownian motion. An asymptotic
analysis is presented for weak surfactant diffusion and weak van der Waals attraction.
In the absence of surfactant diffusion, collision efficiencies for surfactant-covered
bubbles are higher than for rigid spheres in straining flow and lower in shear flow. In
shear flow, the collision efficiency vanishes for surfactant diffusivities below a critical
value if van der Waals attraction is absent.
Linear double-diffusive–inertial instability at the equator
Authors: EDWARDS N. R. , RICHARDS K. J.
Published: July 2002

Motivated by observations of interleaving in the equatorial Pacific, we consider the
linear stability of a basic state on an equatorial β-plane which is susceptible to both
double-diffusive interleaving, driven by a meridional salinity gradient, and inertial
instability driven by meridional shear. In a parameter regime compatible with the
observations strong interaction can occur between the two processes, indicating that
the stability of the system is dependent on the meridional gradients of both salinity
and zonal velocity. Meridional shear is found to enhance the interleaving motion even
for values of shear well below the cutoff for inertial instability. In the presence of
diffusion inertial instability can also be excited by vertical shear, but only if the shear
is comparable to the buoyancy frequency. When double-diffusive driving is weak
relative to inertial driving the growth can be oscillatory, in which case the mechanism
for instability is viscous–diffusive. In this case interleaving layers can slope downwards
towards the fresh side of the front in the fingering regime, inhibiting their own growth.
Effect of entrained bubbles on the structure of vortex rings
Authors: SRIDHAR G. , KATZ J.
Published: July 2002

The effect of entrained bubbles on the structure of a vortex ring is studied using
particle image velocimetry. Quantitative information on the velocity and vorticity
distribution within the vortex core is obtained from multiple images recorded with
two 65 frames per second, 35 mm cameras. Bubble trajectories and velocities are
also determined from these images. It is demonstrated that for certain combinations
of vortex strengths and bubble diameters, a few microscopic bubbles, at very low
overall void fraction, shift and macroscopically deform the structure of the vortex.
For example, five 512 μm diameter bubbles, entrained by a vortex with core diameter
of 2 cm and strength of 160 cm2 s−1,
displace the core by 3.5 mm and fragment the
core into two regions with peak vorticities that are 20% higher than the original
maximum vorticity. The same phenomenon is observed with laminar, transitional and
turbulent vortices. Dimensional analysis along with the experimental data show that
the distortion is maximum when the bubbles settle, following entrainment by the
vortex, in a region located between 20% and 40% of core radius. The governing dimensionless
parameters and trends are identified and discussed. The vortex distortions
are explained in terms of changes to the liquid momentum caused by the entrainment
of the bubbles. It is argued and proven in detail in Appendix A that the change to
the liquid momentum due to the presence of the bubble is equal to the bubble volume
multiplied by the local stresses that exist in the absence of the bubble. These stresses
include the gravity-induced (buoyancy) and hydrodynamic pressure gradients as well
as viscous stresses. The buoyancy displaces the core of the vortex upward whereas the
force due to hydrodynamic pressure gradients reduces the core size and as a result
increases the vorticity. Estimated distortions agree with the experimental data.
Self-diffusion in sheared suspensions by dynamic simulation
Authors: FOSS DAVID R. , BRADY JOHN F.
Published: July 2002

The behaviour of the long-time self-diffusion tensor in concentrated colloidal dispersions
is studied using dynamic simulation. The simulations are of a suspension
of monodisperse Brownian hard spheres in simple shear flow as a function of the
Péclet number, Pe, which measures the relative importance of shear and Brownian
forces, and the volume fraction, ϕ. Here, Pe =
&γdot;a2/D0, where &γdot; is the shear rate, a
the particle size and D0 = kT/6πηa is the Stokes–Einstein diffusivity of an isolated
particle of size a with thermal energy kT in a solvent of viscosity η. Two simulations
algorithms are used: Stokesian Dynamics for inclusion of the many-body hydrodynamic
interactions, and Brownian Dynamics for suspensions without hydrodynamic
interactions. A new procedure for obtaining high-quality diffusion data based on
averaging the results of many short simulations is presented and utilized. At low
shear rates, low Pe, Brownian diffusion due to a random walk process dominates and
the characteristic scale for diffusion is the Stokes–Einstein diffusivity, D0. At zero Pe
the diffusivity is found to be a decreasing function of ϕ. As Pe is slowly increased,
O(Pe) and O(Pe3/2) corrections to the diffusivity due to the flow are clearly seen in
the Brownian Dynamics system in agreement with the theoretical results of Morris
& Brady (1996). At large shear rates, large Pe, both systems exhibit diffusivities that
grow linearly with the shear rate by the non-Brownian mechanism of shear-induced
diffusion. In contrast to the behaviour at low Pe, this shear-induced diffusion mode
is an increasing function of ϕ. Long-time rotational self-diffusivities are of interest
in the Stokesian Dynamics system and show similar behaviour to their translational
analogues. An off-diagonal long-time self-diffusivity, Dxy, is reported for both systems.
Results for both the translational and rotational Dxy show a sign change from low Pe
to high Pe due to different mechanisms in the two regimes. A physical explanation
for the off-diagonal diffusivities is proposed.
Mexico in the Context of the North American Integration: Major Regional Trends and Performance of Backward Regions
Authors: TAMAYO-FLORES RAFAEL
Published: July 2002

The regional impact of the economic integration between Mexico and
its northern neighbours remains virtually unexplored for Mexico. This research
substantiates what had hitherto been no more than conjectures regarding the
impact of NAFTA on the most laggardly Mexican regions. The southern states
have been unable to share in Mexico's impressive export-growth and attraction
of foreign direct investment (FDI) of the 1990s. Neither the insignificant amount
of fdi received by these states nor the increase in their small export-value level
can be attributed to opportunities created by NAFTA. The strong linkage between
fdi and exports, and the predominance of manufacturing observed at the national
level and in other northern states does not exist there. In the state of Oaxaca
export growth is largely accounted for by a primary commodity whose
production has no foreign investment participation. This local scenario is
consistent with the interregional divergence trend observed since the start of the
process of economic integration.
Quasiparticle invariants and energy transfer
between particles and fields
Authors: SOSENKO PETRO P.
Published: July 2002

The second-order approximation in a quasiparticle description of
magnetized
plasmas is studied. The second-order adiabatic invariant of quasiparticle
motion is found. Global adiabatic invariants for a magnetized plasma are
revealed, and their possible role in energy exchange between particles
and
fields, nonlinear mode cascades and global plasma stability is discussed.
Beam stability in strongly magnetized pair plasmas. Part 2
Authors: ROWE G. W. , ROWE E. T.
Published: July 2002

Wave modes in a strongly magnetized pair plasma slab (beam) embedded
in a pair plasma of different number density are considered for highly relativistic
beam flow relative to the bounding plasma. Approximate analytical results are
obtained and compared with numerical calculations and with the thin-beam approximation
derived in Part 1 [J. Plasma Phys.62, 425–439 (1999)].
Complex charge distributions of dielectric dust grains due to plasma flow
Authors: MANWEILER J. W. , ARMSTRONG T. P. , CRAVENS T. E.
Published: July 2002

We examine the charging of dielectric dust grains embedded in a
plasma. Our work is a continuation and refinement of our previous research into
grain charging problems. In 1993, we discussed preliminary simulation results
regarding the charging and intergrain forces between two dielectric dust
particles [J. W. Manweiler et al., Adv. Space Res. 13,
10175 (1993)]. Then, in
1996, we discussed preliminary results with respect to dust grain charging
within asymmetric plasma conditions and how these affect grain–grain
collisional cross-sections [J. W. Manweiler et al., In: The Physics of Dusty
Plasmas (ed. P. K. Shukla et al.), p. 22. World Scientific, Singapore (1996)].
This work was extended to evaluate how asymmetric charging affects
coagulation rates for dielectric dust grains [J. W. Manweiler et al., In: Physics
of Dusty Plasmas, 7th Workshop (ed. M. Horanyi et al.), p. 12. AIP Conf. Proc.
446 (1998)]. Here we report on the results of a significant refinement to our work
to study the behaviour of a dielectric dust grain in a plasma with a bulk flow.
Since charge transport is inhibited on our dielectric grains, we can examine how
asymmetric plasma distributions affect the symmetry of the charge distributions
that develop on the surfaces of the grains. A dielectric dust grain in
a flowing plasma develops a negative total charge and a dipole moment in its
charge distribution that points upstream. We also use this model to study how
the presence of a nearby dust grain affects the development of a grain's charge
distribution. We demonstrate that a smaller grain–grain separation results in a
reduced net charge on each grain. For grains in a flowing plasma, dipole
moments are unaffected by close approach except when one grain is directly in
the ‘wake’ of the other grain. The studies here show that monopole and dipole
electrostatic forces are present when dust is bathed in flowing plasma. Recent
infrared studies suggest that a large fraction of young stars have dusty
envelopes [G. Schilling, Science286, 66 (1999)].
In the formation of accretion
discs around young stars, dust–plasma interactions are probably important.
Full details on the calculations of the results discussed in this paper are
summarized from a more complete treatment of the subject by Manweiler [PhD
Dissertation, University of Kansas (1997)].
Invertebrate borers in the Mediterranean sea grass Posidonia oceanica: biological impact and ecological implications
Authors: Guidetti Paolo
Published: July 2002

The effects of polychaete (Lysidice ninetta, L. collaris, Nematonereis unicornis (Annelida: Polychaeta)) and limnoriid isopod (Limnoria tuberculata (Crustacea: Isopoda)) borers in the Mediterranean sea grass Posidonia oceanica (Potamogetonaceae) were assessed in the meadows of Olbia and Genoa (western Mediterranean Sea). Borer invertebrates were mainly found into the old leaf sheaths of the sea grass. At Olbia, a mean density of borers (202.6±34.8 ind m−2) significantly higher than at Genoa (23.2±7.3 ind m−2) was observed. In 3.3% of samples from Olbia, large polychaetes and isopods were also observed boring into living plant tissues. Only fractions from 0.8—3.9% of the sheath production was actually removed by borers at the two studied meadows. The fact that sheath weight loss with time was higher at Genoa than at Olbia regardless of the presence of borers suggests that other factors than the activity of such organisms are important in the sheath decay process.
Hydrographic circulation and the dispersal of yolk-sac herring (Clupea harengus) larvae in the Blackwater Estuary
Authors: Fox C.J. , Aldridge J.N.
Published: July 2002

Each spring, a localized stock of herring (Clupea harengus, Teleostei, Clupeidae) spawn in the Blackwater Estuary (Essex, UK). The eggs are laid on a gravel bank (Eagle Bank) at the mouth of the estuary. Incubation takes three to four weeks and, after hatching, the larvae can be caught in the area for several months. In this paper, results are presented from a finite-element circulation model used to simulate tidal and wind driven flow fields for the region. A particle tracking model was then used to simulate the dispersal of young herring larvae, up to first feeding, hatching from the Eagle Bank. The simulations predicted that, over a period of 12 d, around 63% of particles would be retained in the area of the Eagle Bank at high water whilst 22% of particles would be further south towards the Buxey Sands. Over the same time, ∼7% of the particles released would be found in the River Blackwater itself. Imposing a steady state wind of 10 m s−1 from the south-west (the dominant wind direction during spring in this area) or north-east had the effect of moving the majority of particles into the river or offshore to the south respectively.
Spatial dispersion and density of the Paranemonia vouliagmeniensis population in Vouliagmeni Lagoon
Authors: Chintiroglou Chariton-Charles , Antoniadou Chrysanthi , Damianidis Panagiotis
Published: July 2002

A number of biological parameters relevant to the population dynamics of Paranemonia vouliagmeniensis are discussed. The abiotic factors of the lagoon's waters are stable throughout the year. Paranemonia vouliagmeniensis populations follow different patterns of distribution (aggregated or random) in relation to human influence, and can thus become a reliable bioindicator for the lagoon.
Limpet relocation from home-scars in relation to position in group
Authors: Coleman R.A. , Hawkins S.J.
Published: July 2002

The relative frequency and destination of limpets relocating from different home-scar positions in respect to aggregations was determined for a population of limpets in Dorset, UK. Limpets on the outside of groups were the most likely to relocate, next were solitary limpets and limpets on the inside of groups were the least likely to move.
Anonyx sarsi: a major unrecognized scavenger and predator in the intertidal zone
Authors: Ingólfsson A. , Agnarsson I.
Published: July 2002

Anonyx sarsi (Crustacea: Amphipoda) is a widely distributed scavenger and predator in shallow waters of northern seas. It was caught, often in large numbers, in baited traps in the intertidal in Iceland, especially during mid-winter. Although hitherto only sporadically recorded from the intertidal, the species is undoubtedly among the most important carrion feeders there, and probably an important predator as well.
Age and growth of the snipefish, Macrorhamphosus spp., in the Portuguese continental waters
Authors: Borges Lisa
Published: July 2002

Age and growth of the snipefish was studied based on samples collected in the Portuguese continental waters between 1996 and 1998. Analysis was conducted for two species, Macrorhamphosus scolopax and M. gracilis and for both species combined. Total length ranged from 5.5 to 18.2 cm for M. scolopax and from 5.4 to 17.3 cm for M. gracilis. Length–weight relationships were described for M. scolopax (a=0.00401; b=3.127), M. gracilis (a=0.00459; b=3.006) and both combined (a=0.00240; b=3.282). Age estimation, based on otolith observations, resulted in six and five years maximum age attributed to M. scolopax and M. gracilis, respectively. Back-calculation analysis based on a polynomial relation of the otolith radius on total length provided significantly smaller lengths-at-age compared with observed lengths. The von Bertalanffy growth curves fitted to observed lengths-at-age provided parameters of L∞=15.7 cm, K=0.654, t0=−1.066 for M. scolopax; L∞=14.2 cm, K=0.694, t0=−0.954 for M. gracilis and L∞=15.8 cm, K=0.470, t0=−1.408 for both species combined.
Commensalism between a liparid fish (Careproctus sp.) and stone crabs (Lithodidae) photographed in situ using a baited camera
Authors: Yau C. , Collins M.A. , Everson I.
Published: July 2002

The commensal relationship between a snailfish, tentatively identified as Careproctus sp. (Osteichthyes: Liparidae), and the lithodid crab Paralomis formosa (Crustacea: Lithodidae) was photographed in situ using a baited camera vehicle, deployed at depths of 625-1525 m around Shag Rocks and South Georgia in the Southern Ocean. The series of time-lapse photographs taken clearly showed that the small liparid fish `hitched rides' on the crabs, presumably attaching to the dorsal carapace and legs of the crabs by means of their ventral sucking disk. Liparid fish of 20-90 mm total length, corresponding to juveniles and adult sizes, were observed on the crabs and indicate that Careproctus sp. is closely associated with P. formosa for the whole of the life cycle of the fish. Such an association may provide the snailfish with protection from potential predators as well as a means of transport towards food-falls but at no apparent cost to the crabs.
Cephalopod prey of two Ziphius cavirostris (Cetacea) stranded on the western Mediterranean coast
Authors: Blanco C. , Raga J.A.
Published: July 2002

The stomach contents of two Cuvier's beaked whales (Ziphius cavirostris), male and female, stranded on the western Mediterranean coast were analysed. Food consisted exclusively of hard cephalopod remains. The character of this teuthophagous diet agrees with the offshore and deep diving behaviour of Z. cavirostris.
AN ARISTOPHANIC CONTRAST TO PHILIPPIANS 2.6–7
Authors: YOUNG NORMAN H.
Published: July 2002

Commentators often note that the emphasis in Phil 2.6–7 on Christ's selfless giving is quite contrary to pagan concepts of divinity. N. T. Wright, for example, writes that αρπαγμoς, when construed as an abstract noun meaning ‘snatching’, ‘grasping’, or ‘getting’, ‘refers, intransitively, to a particular way of life, namely, that which characterized pagan rulers, and indeed pagan gods and goddesses such as the Philippians might have worshipped in their pre-Christian days’. Yet no commentator to my knowledge has referred to the excellent example of the grasping nature of pagan deities found in Aristophanes’ comedy the Ecclesiazusae (‘Women in Government’).
Costs of intraspecific and interspecific host sharing in acanthocephalan cystacanths
Authors: DEZFULI B. S. , GIARI L. , POULIN R.
Published: July 2002

Larval helminths often share individual intermediate hosts with other larval worms of the same or different species. In the case of immature acanthocephalans capable of altering the phenotype of their intermediate hosts, the benefits or costs of host sharing can be evaluated in terms of increased or decreased probability of transmission to a suitable definitive host. Competitive interactions among the immature stages of acanthocephalans within the intermediate host could create additional costs of host sharing, however. The effects of intraspecific and interspecific interactions were measured in 3 sympatric species of acanthocephalans exploiting a population of the amphipod Echinogammarus stammeri in the River Brenta, Italy. The strength of interactions was assessed from differences in the size achieved by infective cystacanths in the intermediate host. The size of Pomphorhynchus laevis cystacanths was not correlated with host size, whereas the size of Acanthocephalus clavula and Polymorphus minutus cystacanths increased with host size. Reductions in cystacanth size caused by intraspecific competition were only detected in P. laevis, but may also occur in both A. clavula and P. minutus. When co-occurring in the same amphipod with cystacanths of A. clavula, cystacanths of P. laevis attained a smaller size than when they occurred on their own. This effect was not reciprocal, with the size of A. clavula cystacanths not being affected. This supports earlier suggestions that it is adaptive for A. clavula to associate with P. laevis in amphipod intermediate hosts, with both species going to the same fish definitive hosts. In contrast, cystacanths of P. laevis achieved their largest size when they co-occurred in an amphipod with a cystacanth of P. minutus, which has a different definitive host (i.e. birds). These findings suggest that the net benefits of sharing an intermediate host can only be estimated by taking into account both the effects on transmission success and the consequences for cystacanth development.
Schistosoma japonicum: immunolocalization of paramyosin during
development
Authors: GOBERT G. N. , STENZEL D. J. , JONES M. K. , ALLEN D. E. , McMANUS D. P.
Published: July 2002

This paper describes the localization of paramyosin immunoreactivity
in Schistosoma japonicum and represents the first comparative
immunolocalization study among schistosome adult, cercariae and lung schistosomula
by electron microscopy. A polyclonal antibody was utilized to immunolabel
paramyosin or paramyosin-like proteins. Paramyosin was localized within
the muscle layer of all 3 developmental stages. Furthermore, paramyosin
was localized within granules of the post-acetabular glands of cercariae,
and within the tegument matrix and surface of lung schistosomules. Adults
and cercariae did not display any detectable paramyosin on the surface
or within the tegument. The possible functions of paramyosin within S.
japonicum and the relevance of these findings in relation to the reported
protective properties of paramyosin as an anti-schistosome vaccine target
molecule are discussed.
Cloning and characterization of a 150 kDa microsphere
antigen of Theileria parva that is immunologically
cross-reactive with the polymorphic immunodominant molecule (PIM)
Authors: SKILTON R. A. , BISHOP R. P. , WELLS C. W. , SPOONER P. R. , GOBRIGHT E. , NKONGE C. , MUSOKE A. J. , MACKLIN M. , IAMS K. P.
Published: July 2002

To identify the genes encoding novel immunodominant antigens of

Theileria parva a λgt11 library of piroplasm genomic
DNA was immunoscreened with bovine recovery serum and a gene encoding
a 150 kDa antigen (p150) was identified. The
predicted polypeptide contains an N-terminal secretory signal sequence

and a proline-rich region of repeated amino acid
motifs. The repeat region is polymorphic between stocks of
T. parva in both copy number and sequence, and analysis of
the repeat region from 10 stocks of T. parva revealed 5 p150 variants.

A monoclonal antibody (mAb) against the T. parva
polymorphic immunodominant molecule (PIM) cross-reacted with the recombinant

p150. The p150 has sequence
homology with a PIM peptide sequence containing the anti-PIM mAb epitope.

Immunoelectron microscopy demonstrated that the p150 antigen, like PIM,

is located in the microspheres of the sporozoites and is exocytosed
following sporozoite invasion of the host lymphocyte. By
immunoelectron microscopy p150 was subsequently transiently
detectable on the sporozoite surface and in the lymphocyte cytosol.
Immunoblotting showed that p150 is also expressed
by the schizont stage, but at much lower levels compared to the sporozoite.

These results suggest a major role for p150
in the early events of host–sporozoite interaction.
The emergence of drug-resistant malaria
Authors: HASTINGS I. M. , MACKINNON M. J.
Published: July 2002

Stochastic processes play a vital role in the early stages of the
evolution of drug-resistant malaria. We present a simple
and flexible method for investigating these processes and understanding
how they affect the emergence of drug-resistant
malaria. Qualitatively different predictions can be made depending on the
biological and epidemiological factors which
prevail in the field. Intense intra-host competition between co-infecting
clones, low numbers of genes required to encode
resistance, and high drug usage all encourage the emergence of drug resistance.
Drug-resistant forms present at the time
drug application starts are less likely to survive than those which arise
subsequently; survival of the former largely depends
on how rapidly malaria population size stabilizes after drug application.
In particular, whether resistance is more likely
to emerge in areas of high or low transmission depends on malaria intra-host
dynamics, the level of drug usage, the
population regulation of malaria, and the number of genes required to encode
resistance. These factors are discussed in
relation to the practical implementation of drug control programmes.
Characteristics of eosinophilic inclusions within
Schistosoma japonicum eggs
Authors: HIRATA M. , NAKASHIMA T. , FUKUMA T.
Published: July 2002

Although eosinophilic bar- or droplet-like inclusions are frequently
detectable inside eggs deposited in the livers of
Schistosoma japonicum-infected animals, little is known of their
exact nature. In the livers of mice implanted with freshly
laid eggs, inclusion-positive eggs were found in 28·7 and 46·2%
of deposited eggs at 2 and 4 weeks, respectively, after
implantation, but in 4·3% at 5 weeks when most of the eggs had already
degenerated. When the extent of granuloma
formation was investigated, granulomas around inclusion-positive eggs were
smaller than those around negative eggs.
Host factors associated with the formation of inclusion were sought using
in vivo and in vitro studies. Following the
administration of anti-egg antigen serum into egg-implanted mice, no increase
in occurrence of inclusion-positive eggs
was seen. In a co-culture of mature eggs with infected rabbit or mouse
serum, inclusions were rarely found. In contrast,
they were found in 17·9% of eggs in the presence of splenic cells.
The present study is the first to show that there is
decreased granuloma formation in the presence of eosinophilic inclusions
inside eggs and our in vitro study suggests that
host cell–egg interaction is responsible for the formation of inclusions.
PCR-based DNA fingerprinting of Giardia duodenalis
isolates using the intergenic rDNA spacer
Authors: HOPKINS R. M. , CONSTANTINE C. C. , GROTH D. A. , WETHERALL J. D. , REYNOLDSON J. A. , THOMPSON R. C. A.
Published: July 2002

The potential for the non-coding intergenic rDNA spacer (IGS) to DNA fingerprint Giardia duodenalis isolates was
investigated. Conserved PCR primers, specific for the flanking large and small rDNA genes, were used to amplify the IGS
from 52 in vitro-cultured Giardia isolates. Four distinct IGS–PCR size groups (1·35–1–6 kb) were observed, which
correlated closely with the major genetic assemblages established previously for the same isolates using isoenzyme analysis.
IGS–PCR size groups A (1·42 kb), C (1·4 kb) and D (1·35 kb) corresponded to isoenzyme assemblage A, and IGS–PCR
group B (1·6 kb) to isoenzyme assemblage B. Amplified products from IGS–PCR size groups A and B, which contained
50/52 isolates, were subsequently digested with 8 different restriction enzymes and their profiles compared. Analysis
separated isolates within each IGS–PCR size group into 2 distinct clusters which correlated almost exactly with the same
genetic groups established previously using isoenzyme electrophoresis. Within each cluster, both methods exhibited a
similar capacity to distinguish between Giardia genotypes although they established different genetic relationships between
individual isolates. Much of the variability associated with the IGS was attributed to isolates harbouring multiple IGS-
sequence types. Restriction analysis of IGS–PCR products amplified from cloned and parent lines of a human isolate BAH
39, which contains multiple IGS variants, showed that trophozoite populations are homogeneous with respect to the types
of IGS-variants they maintain. Furthermore, in vitro culture of the cloned isolate BAH39c9 over a 6-year period also failed
to reveal variation in IGS–PCR digestion profiles. These results suggest that IGS–PCR RFLP profiles are inherently
stable. IGS–PCR analysis was successfully applied to 11 Giardia cyst samples highlighting the potential for this approach
to genotype Giardia isolates without the need for in vitro culture.
Onchocerca–Simulium complexes in Venezuela: can human
onchocerciasis spread outside its present endemic areas?
Authors: BASÁÑEZ M. G. , YARZÁBAL L. , FRONTADO H. L. , VILLAMIZAR N. J.
Published: July 2002

The compatibility between sympatric and allopatric combinations of Onchocerca volvulus–anthropophilic species of
Simulium was studied in the north-eastern focus of human onchocerciasis as well as in a densely populated locality of the
Amazonas State in Venezuela. The objectives were to test the conjecture that local adaptation exists between the parasite
and its vectors (the Onchocerca–Simulium complex hypothesis), and assess the possibility of the infection spreading from
its present distributional range. For the homologous combination, O. volvulus–S. metallicum cytospecies E in Anzoátegui
State (north-eastern focus), parasite yield was 45% in contrast to 1% for the heterologous, southern parasite–S. metallicum
infection. This was significantly lower than the parasite yield (4–10%) expected after allowing for the effect of density-dependent limitation of infective larval output described in this paper for S. metallicum. The population of S. exiguum s.l.
from southern Venezuela allowed no larval development beyond the L1 stage of either northern or southern parasites.
Mechanisms for such refractoriness probably operate at the level of the thoracic muscles, not affecting microfilarial uptake
or migration out of the bloodmeal. The parasite yield of southern O. volvulus in S. oyapockense s.l. flies biting man at
Puerto Ayacucho (Amazonas) was about 1%, in agreement with the figures recorded for highly compatible sympatric
combinations such as O. volvulus–S. ochraceum s.l. in Guatemala. No infective larval development of the northern parasite
was observed in southern S. oyapockense. These results, together with considerations of typical worm burdens in the
human host, presence/absence of armed cibaria in the simuliids, parasite-induced vector mortality, and fly biting rates,
suggest a lower potential for onchocerciasis to spread between the northern and southern endemic areas of Venezuela than
that between Amazonian hyperendemic locations and settlements outside this focus with high densities of S. oyapockense
s.l.
Our Place in the Cosmos
Authors: Leslie John
Published: July 2002

Our world seems fine tuned in life-permitting ways. If the cosmos contains many universes, only the appropriately tuned ones can be seen by living beings. An alternative is that God acted as Fine Tuner. We might account for God in terms of an eternally powerful ethical requirement that God exists, rejecting J. L. Mackie's judgment that absolute ethical requirements are incredibly queer. Mackie viewed such requirements as logically possible, so if they were absent then this would seem a matter of synthetic necessity. Again, if they existed then their creative effectiveness would, Mackie thought, be logically possible. Their actual ineffectiveness would thus involve a further synthetic necessity. Theists could maintain that the synthetic necessities were instead ones making ethical requirements real and creatively powerful. Yet why, then, would there exist anything but divine knowledge of everything worth knowing? A spinozistic answer is that such knowledge is all that exists.
Literature, Truth and Logic
Authors: Warner Martin
Published: July 2002

Analytic philosophy's characteristic downgrading of literature's putative concern with truth, and envisaging of its interest to philosophy merely in terms of material for logical analysis, was prefigured by Frege. The initial plausibility of this approach was in part a function of certain preferred models of philosophy as analysis which were themselves deeply flawed. An exploration of their weaknesses in the light of more adequate theories of language, truth and logic enables us to give proper weight both to rhetorical and imaginative aspects of philosophical discourse, and to the capacity of works of literature to bear on issues of truth—and thereby contribute to philosophical understanding.
Citizenship in the New Welfare Market: the Purposes
of Housing Advice Services
Authors: DEAN JO , GOODLAD ROBINA , ROSENGARD ANN
Published: July 2002

In current debates about citizenship, three approaches to social rights
can be detected. Three models of access to social rights mirror these
accounts. The institutionalised rights model, based on the post-war welfare
state, stresses education and information. The market efficiency model,
stressing the need for consumer information, stems from contemporary
neo-liberal, consumerist approaches to welfare provision. The radical
model challenges the assumption of a level playing field for all citizens.
As the state's role in housing has been transformed and governments
have stressed the market efficiency model, housing advice services have
expanded in both state and voluntary sectors. The objectives and work
of these services is examined and shown as providing a close fit with
the institutionalised rights model in the local authority sector, while in
the voluntary sector the radical rights model dominates. In addition, the
campaigning work of voluntary organisations is shown to promote a
radical view of citizenship rights.
Per Linell, Approaching dialogue: Talk,
interaction and contexts in dialogical perspectives.
(Impact: Studies in language and society, 3.) Amsterdam &
Philadelphia: Benjamins, 1998. Pp. xvii, 330. Hb $85.00.
Authors: Keating Elizabeth
Published: July 2002

Linell argues that dialogism is the crucial path to
theorizing and understanding discourse, cognition, and
communication – particularly the study of conversation
and other kinds of talk-in-interaction. One of the goals
of his book is to develop an “empirically valid form
of dialogism,” as opposed to an idealistic one, through
the empirical investigation of communication. Linell develops
a theory of “communicative projects,” a notion
which incorporates aspects of individual agency as well
as the idea of talk as emergent, collaborative work by
co-present individuals. The notion of “communicative
projects” is meant as a bridge across the oft-cited
polarity between “micro” and “macro”
– or as Linell formulates it, between “elementary
contributions and local sequences on the one hand, and
the global and more abstract notions of activity types
and communicative genres.”
John H. McWhorter, Towards a new model of creole
genesis. (Studies in ethnolinguistics, 3.) New York:
Lang, 1997. Pp. xiii, 199. Hb $44.95.
Authors: Winford Donald
Published: July 2002

This is an informative and quite stimulating book,
which offers a detailed look at the nature of creole genesis
with particular emphasis on the emergence of Saramaccan
(SM), one of the maroon creoles spoken in Suriname. McWhorter
describes himself in the preface as a member of the third
generation of creolists – a generation not afraid
to challenge the conventional wisdom in the field, or to
offer alternative theories. This book has the rather ambitious
aim of proposing a “systematic account of creolization
which integrates a number of the processes which creolists
have identified as contributing the structural form of
these languages” (10). In pursuing it, McWhorter
re-examines two key areas of SM syntax – serial verb
constructions and the copula system – to support
his own eclectic view of creole formation. Despite the
date of publication, the book is essentially the same as
McWhorter's doctoral dissertation, completed in 1993.
Hence it is somewhat dated, and omits mention of much recent
and current work on creole genesis.
Srikant Sarangi & Celia Roberts (eds.), Talk,
work and institutional order: Discourse in medical, mediation,
and management settings. Berlin: Mouton de Gruyter
(Language, Power and Social Process Series), 1999. Pp.
530. Pb 24.00.
Authors: Mondada Lorenza
Published: July 2002

This very interesting and useful book proposes
an interdisciplinary approach to professional talk and
its constitutive role in various institutional settings.
It aims at reviewing the available literature and at providing
theoretical insights and methodological tools for further
analyses, thereby building possible bridges between academic
research and its practical relevance within institutions.
Evaluating the relationship between REM and memory consolidation: A need for scholarship and hypothesis testing
Authors: Smith Carlyle , Rose Gregory M.
Published: July 2002

The function of REM, or any other stage of sleep, can currently only be conjectured. A rational evaluation of the role of REM in memory processing requires systematic testing of hypotheses that are optimally derived from a complete synthesis of existing knowledge. Our view is that the large number of studies supporting a relationship between REM-related brain activity and memory is not easily explained away.

[Vertes & Eastman]
Efficiency, information theory, and neural representations
Authors: Devlin Joseph T. , Davis Matt H. , McLelland Stuart A. , Russell Richard P.
Published: July 2002

We contend that if efficiency and reliability are important factors in neural information processing then distributed, not localist, representations are “evolution's best bet.” We note that distributed codes are the most efficient method for representing information, and that this efficiency minimizes metabolic costs, providing adaptive advantage to an organism.
Locality, modularity, and computational
neural networks
Authors: Bischof Horst
Published: July 2002

There is a distinction between locality and modularity. These
two terms have often been used interchangeably in the target article
and commentary. Using this distinction we argue in favor of a
“weak” modularity. In addition we also argue that both
PDP-type networks and box-and-arrow models have their own strengths
and pitfalls.
Are multiple fixations necessarily deictic?
Authors: Bogacz Sally
Published: July 2002

The motor system might well use deictic strategies when
subjects learn a new task. However, its not clear that Ballard et al.
show this. Multiple eye-fixations may have little to do with deixis
and more to do with the unfamiliarity of the task. In any case, deixis
does not entail embodiment, since a disembodied Cartesian brain could
use deictic strategies.
Cognition without representational redescription
Authors: Bryson Joanna , Lowe Will
Published: July 2002

Ballard et al. show how control structures using minimal state
can be made flexible enough for complex cognitive tasks by using
deictic pointers, but they do so within a specific computational
framework. We discuss broader implications in cognition and memory
and provide biological evidence for their theory. We also suggest an
alternative account of pointer binding, which may better explain their
limited number.
Epistemological missing links
Authors: Dartnall Terry
Published: July 2002

Clark & Thornton's “superficially distinct
ploys and mechanisms” are in fact very different: there is a
deep difference between (a) filters and feature detectors, which
“let the information in,” and (b) contentful
representations and theories, which reconfigure it into a
computationally tractable form. (a) is bringing abilities
to experience whereas (b) is bringing content to experience.
Both have well known problems. I outline an evolutionary story that
avoids these problems and begins to explain how representations and
theories developed out of feature detectors and filters.
Semantic memory
Authors: McNamara Timothy P.
Published: July 2002

Glenberg tries to explain how and why memories have semantic
content. The theory succeeds in specifying the relations between two
major classes of memory phenomena – explicit and implicit memory
– but it may fail in its assignment of relative importance to
these phenomena and in its account of meaning. The theory is syntactic
and extensional, instead of semantic and intensional.
Constructivism: Can directed mutation improve on classical neural selection?
Authors: Reeke George N.
Published: July 2002

Quartz & Sejnowski (Q&S) find flaws in standard
theories of neural selection, which they propose to repair by
introducing Lamarckian mechanisms for anatomical refinement that
are analogous to directed mutation in evolution. The reversal of cause
and effect that these mechanisms require is no more plausible in an
explanation of cognition than it is in an explanation of
evolution.
Statistical significance testing was not meant for weak corroborations of weaker theories
Authors: Bookstein Fred L.
Published: July 2002

Chow sets his version of statistical significance testing in
an impoverished context of “theory corroboration”
that explicitly excludes well-posed theories admitting of strong support by precise empirical evidence. He demonstrates no scientific
usefulness for the problematic procedure he recommends instead.
The important role played by significance testing in today's
behavioral and brain sciences is wholly inconsistent with the rhetoric
he would enforce.
Explaining exceptional performance: Constituent abilities and touchstone phenomena
Authors: Charness Neil
Published: July 2002

Investigations of innate talent should narrow the definition
of talent to deal with constituent abilities, identify touchstone
phenomena, and provide detailed explanations of these phenomena.
A list of relevant phenomena is proposed.
Metric assumptions are neither necessary nor sufficient to describe similarities
Authors: Gregson Robert A. M.
Published: July 2002

Alternative models of similarity judgments that do not rest on
metric space assumptions are known to be better descriptions of actual
human behaviour but are ignored by Edelman. The internal spaces he
postulates are a convenient fiction for artificial intelligence, but
not compatible with what is now known about psychophysics at
both behavioural and neurological levels of perceptual
processing.
Linking spread of neural activity and filling-in: A few more arguments in favor
Authors: De Weerd Peter
Published: July 2002

This commentary sides with Pessoa and his colleagues in
arguing that some types of perceptual filling-in are linked with a
spread of cortical activity, a hypothesis that has often been rejected
on philosophical grounds. Some recent data are discussed that
strengthen this linking hypothesis and indicate that a spread of
cortical activity may be essential for normal surface
perception.
Is relational complexity a useful metric for cognitive development?
Authors: Goswami Usha
Published: July 2002

This commentary focusses on the evidence used by Halford
et al. to support their postulated links between relational complexity
and age differences in children's understanding of concepts.
None of their developmental claims is consistent with recent
cognitive-developmental research. Relational complexity must
be an important variable in cognition, but it does not provide a
satisfactory metric for explaining cognitive development.
Resisting the tyranny of terminology: The general dynamical hypothesis in cognitive science
Authors: Horgan Terence , Tienson John
Published: July 2002

What van Gelder calls the dynamical hypothesis is only a
special case of what we here dub the general dynamical hypothesis.
His terminology makes it easy to overlook important alternative
dynamical approaches in cognitive science. Connectionist models
typically conform to the general dynamical hypothesis, but not to
van Gelder's.
Extensional assumptions in theories of meaning and concepts
Authors: Murphy Gregory L.
Published: July 2002

The problems that Millikan addresses in theories of concepts
arise from an extensional view of concepts and word meaning.
If instead one assumes that concepts are psychological entities
intended to explain human behavior and thought, many of these
problems dissolve.
Nature's subtlety undermines the empirical relevance of both dynamical and computational hypotheses
Authors: Mulhauser Gregory R.
Published: July 2002

Technical hitches mar van Gelder's proposed map of the
conceptual landscape, particularly with respect to descriptive levels
and the trio of instantiation, realisation, and implementation.
However, for all the formal quibbles, van Gelder is onto something
important; the tension he notes between computationalism and a
dynamical alternative threatens to transform the way we conduct
cognitive science research.
The dynamics of language
Authors: Culicover Peter W. , Nowak Andrzej
Published: July 2002

To deal with syntactic structure, one needs to go beyond a
simple model based on associative structures, and to adopt a dynamical
systems perspective, where each phrase and sentence of a language
is represented as a trajectory in a syntactic phase space. Neural
assemblies could possibly be used to produce dynamics that in
principle could handle syntax along these lines.
A wiring demon meets socialized humans and calibrated photometers
Authors: Brill Michael H.
Published: July 2002

Ignoring consciousness, I apply Palmer's ideas to a photometer, for which calibration is analogous to socialization of humans to agree in color. Some attributes of the photometer – such as its aperture – do not need to be known because their values are transparent to calibration. But a writing demon can wreak havoc if it permutes measured values before interpolation completes calibration – as happens in Palmer's color rewirings.
The dual nature of the language faculty
Authors: Clahsen Harald
Published: July 2002

The following discussion aims to illuminate further the way in which morphologically complex words are represented in the mental lexicon. It is argued that the dual-mechanism model can accommodate the linguistic and psycholinguistic evidence currently available, not only on German inflection (as pointed out in the target article) but also on other languages (as presented in several commentaries). Associative single-mechanism models of inflection, on the other hand, provide only partial accounts.
On Gromov's theory of rigid transformation groups: a dual approach
Authors: ZEGHIB ABDELGHANI
Published: July 2002

Geometric problems are usually formulated by means of (exterior) differential systems. In this theory, one enriches the system by adding algebraic and differential constraints, and then looks for regular solutions. Here we adopt a dual approach, which consists of enriching a plane field, as this is often practised in control theory, by adding brackets of the vector fields tangent to it and, then, looking for singular solutions of the obtained distribution. We apply this to the isometry problem of rigid geometric structures.
The $\bm{n}$-point correlations between values of a linear form
Authors: MARKLOF JENS
Published: July 2002

We show that the $n$-point correlation function for the fractional parts of a random linear form in $m$ variables has a limit distribution with power-like tail. The existence of the limit distribution follows from the mixing property of flows on ${\rm SL}(m+1,{\Bbb R})/{\rm SL}(m+1,{\Bbb Z})$. Moreover, we prove similar limit theorems (i) for the probability to find the fractional part of a random linear form close to zero and (ii) also for related trigonometric sums. For large $m$, all of the above limit distributions approach the classical distributions for independent uniformly distributed random variables.