bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis and control of redundant manipulator dynamics based on an
extended operational space
Authors: Park Ki Cheol , Chang Pyung-Hun , Lee Sukhan
Published: August 2008

In this paper a new concept, named the
Extended Operational Space (EXOS), has been proposed for the effective
analysis and the real-time control of the robot manipulators with
kinematic redundancy. The EXOS consists of the operational space (OS)
and the optimal null space (NS): the operational space is
used to describe manipulator end-effector motion; whereas the optimal null
space, described by the minimum number of NS vectors, is
used to express the self motion.

Based upon the EXOS formulation,
the kinematics, statics, and dynamics of redundant manipulators have been
analyzed, and control laws based on the dynamics have been
proposed. The inclusion of only the minimum number of NS
vectors has changed the resulting dynamic equations into a very
compact form, yet comprehensive enough to describe: not only the
dynamic behavior or the end effector, but also that of
the self motion; and at the same time the interaction
of these two motions. The comprehensiveness is highlighted by the
demonstration of the dynamic couplings between OS dynamics and NS
dynamics, which are quite elusive in other approaches.

Using the proposed
dynamic controls, one can optimize a performance measure while tracking
a desired end-effector trajectory with a better computational efficiency than
the conventional methods. The effectiveness of the proposed method has
been demonstrated by simulations and experiments.
Sliding mode control with perturbation estimation: application on DD robot
mechanism
Authors: Curk Boris , Jezernik Karel
Published: August 2008

In this work another perturbation estimation sliding
mode based control algorithm is introduced for a class of
robotic systems in the presence of structured and unstructured uncertainties
and external disturbances. The effects of these uncertainties are combined
into a single quantity. A full order device with the
actuator voltages as control inputs is assumed in control design.
The decentralized control scheme with only a partial state feedback
is applied. A modification of the switching functions with perturbation
estimation is introduced. The salient features of this approach is
that the perturbations are effectively treated by a computationally straightforward
procedure. The proposed controller is applied to a minimal configuration
direct drive robot mechanism.
Dynamic modelling of a single-link flexible manipulator: parametric and non-parametric approaches
Authors: Shaheed M.H. , Tokhi M.O.
Published: August 2008

This paper presents an investigation into the development of parametric and non-parametric approaches for

dynamic modelling of a flexible manipulator system. The least mean

squares, recursive least squares and genetic algorithms are used to

obtain linear parametric models of the system. Moreover, non-parametric models

of the system are developed using a non-linear AutoRegressive process

with eXogeneous input model structure with multi-layered perceptron and radial

basis function neural networks. The system is in each case

modelled from the input torque to hub-angle, hub-velocity and end-point

acceleration outputs. The models are validated using several validation tests.

Finally, a comparative assessment of the approaches used is presented

and discussed in terms of accuracy, efficiency and estimation of

the vibration modes of the system.
Feedback control for object manipulation by a pair of soft tip fingers
Authors: Doulgeri Z. , Fasoulas J. , Arimoto S.
Published: August 2008

This

paper discusses the problem of stable grasping and object manipulation

by a pair of robot fingers when fingertips are covered

with soft compressible material and fingers are allowed to incline

their last link against the object surface. The area contact

between the fingertips and the rigid object surface leads to

nonholonomic constraints even for the planar case; however, the variational

principle can be applied and the equation of motion is

derived as a set of nonlinear differential equations with extra

terms of Langrange multipliers incorporating the constraints. The proposed feedback

controller is a linear combination of simple feedback control signals

each designed for realizing grasp stabilization, regulation of object rotation

and regulation of object position respectively. The controller is shown

to achieve asymptotic convergence to the desired state at a

stable grasping configuration. Simulation results are presented confirming the theoretical

findings.
The effects of parameter variation on the gaits of passive walking models: simulations and experiments
Authors: Ning Liu , Junfeng Li , Tianshu Wang
Published: August 2008

We have made a systematic study of the gait of a straight leg planar passive walking model through simulations and experiments. Three normalised parameters, which represent the foot radius, the position of the mass centre and the moment of inertia, are used to characterise the walking model.

In the simulation, we have obtained the fixed points and the basins of attraction of the walking models with different parameter combinations by the aid of the cell mapping method. With the results of fixed points, we investigated the effects of parameter variations on the gait descriptors, including step length, period, average speed and energy inefficiency. A model that has a large basin of attraction has been obtained, and it can start walking far from its fixed point. However, the size of the basin of attraction is not a good measurement of robustness. Thus, we proposed floors with random slope angles or stairs with random heights to test robustness. Five hundred times of simulations with 100 non-dimensional time units were implemented for each parameter combination. The times that the walker failed to arrive at the end were recorded. The simulation results showed that the model with a larger foot radius and higher position of mass centre has a lower possibility of falling on uneven floors. A large moment of inertia is helpful for walking on a random slope angle floor, while low values of moment of inertia are good for navigating random stairs.

Prototype experiments have validated the simulation results, which showed that models with larger feet have a longer step length and high speed. However, period differences were difficult to obtain in the experiments since the differences were very small. We have tested the sensitivity with the initial conditions of the models with different foot radii on a flat floor, and have also tested the robustness of the models on a floor with random slope angles. The times that the model reached the end of the floor were recorded. The experimental results showed that a large foot radius is good for improving the basin of attraction and robustness on uneven floors. Finally, the exceptions of the experiment are explained.
A new calibration method for industrial robots
Authors: Karlsson Björn , Brogårdh Torgny
Published: August 2008

This paper presents a new calibration
method for industrial robots. The calibration method is based on
a combination of inclinometer and LVDT measurements and is very
simple to use. The inclinometers measure the deviation from the
gravity direction of a measurement rod and the LVDT sensor
measures the length of the rod. The inclinometers can be
used without any pre-calibration and the whole equipment is inexpensive,
portable and robust.
Performance, Embodiment, Voice: the Theatre/Dance Cross-overs of Dodin, Bausch, and Forsythe
Authors: Shevtsova Maria
Published: August 2008

The closing decades of the twentieth century and the opening years of the twenty-first have seen a wide range of hybrid and cross-over performance forms, dance/theatre being prominent among them. In this article, Maria Shevtsova outlines the similarities between the working principles of director Lev Dodin and those of the choreographers Pina Bausch and William Forsythe, suggesting how they have set and still exemplify current trends in a networked world (Castells) of precarity (Bourdieu) and uncertainty. She also explores a broader socio-artistic context for her focus. This text is a slightly modified version of a belated inaugural lecture for her third appointed professorial chair, at Goldsmiths College, University of London, in March 2002. Maria Shevtsova is an Advisory Editor of NTQ, whose recent publications include ‘Theatre and Interdisciplinarity’ (2001), a special issue she guest-edited for Theatre Research International, and ‘The Sociology of the Theatre’ (2002), edited for Contemporary Theatre Review, which includes her essay, ‘Appropriating Pierre Bourdieu's Champ and Habitus for a Sociology of Stage Productions’. Her book on Lev Dodin and the Maly Drama Theatre of St Petersburg is due for publication in 2003.
The Maker and the Tool: Charles Parker, Documentary Performance, and the Search for a Popular Culture
Authors: Watt David
Published: August 2008

Charles Parker's BBC Radio Ballads of the late 1950s and early 1960s, acknowledged by Derek Paget in NTQ 12 (November 1987) as a formative influence on the emergence of what he called ‘Verbatim Theatre’, have been given a new lease of life following their recent release by Topic Records; but his theatrical experiments in multi-media documentary, which he envisaged as a model for ‘engendering direct creativity in the common people’, remain largely unknown. The most ambitious of these – The Maker and the Tool, staged as part of the Centre 42 festivals of 1961–62 – is exemplary of the impulse to recreate a popular culture which preoccupied many of those involved in the Centre 42 venture. David Watt, who teaches Drama at the University of Newcastle, New South Wales, began researching these experiments with work on a case study of Banner Theatre of Actuality, the company Parker co-founded in 1973, for Workers' Playtime: Theatre and the Labour Movement since 1970, co-authored with Alan Filewod. This led to further research in the Charles Parker Archive at Birmingham Central Library, and the author is grateful to the Charles Parker Archive Trust and the staff of the Birmingham City Archives (particularly Fiona Tait) for the opportunity to explore its holdings and draw on them for this article.
Archive or Memory? The Detritus of Live Performance
Authors: Reason Matthew
Published: August 2008

The positive valuation of theatre as live performance, and therefore also its transience, is frequently accompanied by the urgent expression of the need to counter that transience by means of documentation. This desire to ‘save’ theatre reaches its most fervent expression (and hope of authority and permanence) with the live performance archive. Archive theory, however, now insists on the instability and uncertainty of the archive, which not only documents but also constructs its subject. In this article, Matthew Reason argues that, by tracing comparisons between archives and human memory, it is possible to establish a new formulation of the archive – as detritus, not completeness – that puts a value on mutability as a reflection of theatre's liveness. Matthew Reason is currently completing a PhD on representations of live performance at the University of Edinburgh. He has edited a special edition of the Edinburgh Review (ER106) on Theatre in Scotland, and has previously worked at the Edinburgh International Festival, where his responsibilities included maintaining the archive.
Bat community structure at Iwokrama Forest, Guyana
Authors: LIM BURTON K. , ENGSTROM MARK D.
Published: August 2008

With 86 species, Iwokrama Forest in central Guyana has the highest reported bat biodiversity for a protected area in the world. Using standardized capture data for 73 of these 86 species, we document community structure of bats in terms of species diversity, relative abundance, gross biomass, feeding guilds, vertical stratification and a trophic-size niche matrix. Based on faunal surveys in 1997, with similar amounts of effort in the forest canopy and at ground level, the greater fruit-eating bat (Artibeus lituratus) was by far the most ecologically dominant species in terms of frequency of capture and biomass. In total, frugivores comprised 70% of the species diversity and 78% of the biomass. The most common species of bat were fully partitioned in a resource niche matrix of size and trophic guild when vertical stratification was included as a variable. We conclude that resource partitioning and species packing differentially affect relative size in tropical bats, and are better summarized and analysed in three dimensions.
Allometric differentiation among tropical tree seedlings in heath and peat-swamp forests
Authors: NISHIMURA TAKASHI B. , SUZUKI EIZI
Published: August 2008

Above- and below-ground morphology of seedlings (up to 98 cm in height) were compared by allometric
analyses in tropical heath forest and peat-swamp forest in Central Kalimantan. Thirteen abundant species were selected,
including two species found in both forests. In above-ground morphology, heath forest seedlings invested more in leaf
mass, while peat-swamp forest seedlings invested more in stem mass, stem height, crown area and leaf area. In
below-ground morphology, heath forest seedlings invested more in root mass and depth, while peat-swamp forest
seedlings invested more in lateral development of the root system. Both specific leaf area and area per leaf of heath
forest seedlings were lower than those of peat-swamp forest seedlings. This differentiation in seedling morphology
between forest types was evident as a plastic response in the two shared species. Heath forest seedlings on coarse-textured bleached sand with low water retention suffer occasional drought whereas peat-swamp forest seedlings on
waterlogged peat rarely experience drought. We concluded that seasonal water limitation brought about the convergence in seedling morphology within heath forest because average understorey irradiances and soil nutrient concentration were assumed to be similarly low in both forests.
Morph-specific correlations between floral traits in a distylous Ophiorrhiza napoensis (Rubiaceae) population in southern China
Authors: KUDOH HIROSHI , SUGAWARA TAKASHI , WU SUGONG , MURATA JIN
Published: August 2008

Floral trait correlations were compared between the two flower morphs of a distylous Ophiorrhiza napoensis population in a subtropical evergreen forest at the Defu Natural Animal Preserve, Guangxi, China. Common principal component analyses indicated that overall patterns in correlations among floral traits were morph specific in the study population. Strong positive correlations (r > 0.9) between anther height and corolla-tube length were found in both morphs. Stigma height correlated positively with corolla-tube length in the long-styled morph (r = 0.843), but not in the short-styled morph (r = −0.018). Flower-morph-specific correlation suggests that natural selection by pollinators has moulded trait covariance among floral traits. Because morph-specific correlations are expressed as the patterns of within-morph variation among multiple traits, putative genes responsible for the stigma-corolla tube correlation should not link to the supergene for sex-organ reciprocity between the morphs, but their expression is limited in the long-styled morph.
Seed dispersal by a diurnal primate community in the Dja Reserve, Cameroon
Authors: POULSEN JOHN R. , CLARK CONNIE J. , SMITH THOMAS B.
Published: August 2008

Multiple species of primate disperse seeds and differentially contribute to the seed rain in tropical forests. The goal of this study was to examine seed dispersal by a primate community of five monkey and two ape species in the Dja Reserve, Cameroon. The density of primates in the reserve was calculated to be 77 individuals km-2. Analysis of 5789 faecal clumps demonstrated that 40% of monkey and 74% of ape faecal clumps possessed whole seeds. Six of the seven focal species acted as seed dispersers; faecal clumps passed by the black-and-white colobus (Colobus guereza) did not contain any whole seeds during the study. Seed passage trials on four captive monkey species showed monkeys to have an average seed passage time of 22 hours and defecation rate of five times per day. From the above results, the primate community was estimated to defecate 1129 seeds km-2 d-1. Seeds passed by the primate community came from 125 species of trees, lianas and shrubs, equivalent to at least 34% of the known tree flora. Rarefaction curves indicated that additional collection effort would identify more seed species passed by primates. Germination studies demonstrated that primate-passed seeds are viable. The number of seeds and plant species dispersed suggests that the primate community plays an important role in the maintenance of forest structure.
Agreement between floristic and soil organic carbon isotope (13C/12C, 14C) indicators of forest invasion of savannas
during the last century in Cameroon
Authors: GUILLET BERNARD , ACHOUNDONG GASTON , HAPPI JOSEPH YOUTA , BEYALA VÉRONIQUE KAMGANG KABEYENE , BONVALLOT JACQUES , RIERA BERNARD , MARIOTTI ANDRÉ , SCHWARTZ DOMINIQUE
Published: August 2008

In an area of savanna-forest (S-F) mosaic of Cameroon, at Kandara near Bertoua, an enclosed savanna
bordered by young semi-deciduous forests was selected for detailed studies of vegetation and soil carbon isotope
compositions with a view to estimating the rate of forest advance into savannas. Forest floristic composition and
structure were analysed in small plots along two S-F transects and within two large stands. Tree species counts and
basal area (BA) measurements gave convergent results defining (1) an edge forest with low BA values that forms an
irregular strip parallel to the S-F border, (2) a large colonization zone zone composed of pioneer species (Albizia
species, with individuals of very large diameter) and (3) a mature forest composed of abundant Rinorea individuals
and large individuals of Triplochiton scleroxylon and Piptadeniastrum africanum. Carbon stable isotopes were deter
mined from organic matter of soil profiles sampled at various depths in savanna, colonization-zone and mature forest.
In the deep soil horizons (40-50 cm) of the colonization-zone profiles, δ13C values similar to those of the present
savanna reveal the past existence of a large-tree savanna. In subsurface horizons (15-20 cm), δ13C values intermediate
between those of savanna and mature forest prove the encroachment of the forest ecosystem on savanna. Using 14C
measurements, the mean residence time (MRT) of soil organic matter of these last horizons was determined with
precision owing to the atmospheric 14C pulse from nuclear bomb tests prior to 1964. By assuming an exponential age
distribution of organic compounds and by taking account of MRT and remaining carbon from the savanna, the coloniza
tion zone was found to be 60-80 y old. The age of the colonization zone being the same near the present savanna and
near the mature forest, it seems that the forest advance was probably not a linear process but would result from the
coalescence of Albizia thickets born in savanna.
Low rates of background canopy-gap disturbance in a seasonally dry forest in the Yucatan Peninsula with a history of fires and hurricanes
Authors: DICKINSON MATTHEW B. , HERMANN SHARON M. , WHIGHAM DENNIS F.
Published: August 2008

Isolated canopy gaps involving one to several trees occur continuously and frequently in many moist and wet neotropical forests (sensu Holdridge et al.1971), shaping tree community structure through a shifting mosaic of patches of high resource availability for small and young trees (Denslow 1980). Though there are few relevant data (Jans et al. 1993), forests with significant seasonal drought are expected to have lower rates of canopy-gap formation (gaps ha-1 γ-1), smaller gap sizes, and, thus, lower rates of canopy disturbance (%γ-1, see review in Whigham et al. 1999). At the extreme, very dry tropical forests do not appear to fit the gap-phase dynamics concept (Swaine et al. 1990).
Demography of the Brazil nut tree (Bertholletia excelsa) in the Bolivian Amazon: impact of seed extraction on recruitment and population dynamics
Authors: ZUIDEMA PIETER A. , BOOT RENÉ G. A.
Published: August 2008

A demographic study was carried out on Bertholletia excelsa, the Brazil nut tree, in two primary forest

sites in Northern Bolivia where Brazil nuts have been harvested for several decades. In spite of the large proportion

(93%) of seeds that are harvested, reasonable densities of recently emerged seedlings were found. Seeds of Bertholletia

are contained in woody fruits that are primarily opened by agoutis. Most fruits are left untouched on the forest floor

for 1–2 y before they are opened, possibly due to high energetic costs of fruit opening just after fruit fall. However,

the proportion of viable seeds is strongly reduced in older fruits.

Growth in diameter at breast height (dbh) was low for pole-sized trees (< 15 cm dbh) and adult trees (> 100 cm

dbh) and peaked for intermediate-sized trees (30–60 cm). These trees often attained a growth rate of > 1.5 cm y−1,

which is high compared with other non-pioneer tropical trees. This, and the strong growth response to increased light

availability found for seedlings and saplings, suggest that Bertholletia excelsa can be classified as a gap-dependent

species. Matrix population models were constructed for both study populations. Population growth rates (λ) were close

to one, and were most sensitive to persistence in one size category. Age estimates revealed that age at first reproduction

(at dbh > 60 cm) amounts to over 120 y, and age in the last category (dbh > 160 cm) to almost 300 y. Given the

continuous rejuvenation of the population, the stable population size, the high age at maturity and the long reproductive

period, it is concluded that current levels of Brazil nut extraction may be sustained at least for several decades and

perhaps for even longer periods.
Regeneration patterns among bird-dispersed plants in a fragmented Afrotropical forest, south-east Kenya
Authors: GITHIRU MWANGI , BENNUN LEON , LENS LUC
Published: August 2008

Fruit-eating birds play an important role in the seed dispersal of many tropical plants (e.g. Herrera 1984), and the foraging behaviour of avian frugivores may affect their seed-dispersal capabilities (Loiselle & Blake 1999,Schupp 1993, Traveset 1994). For instance,shorter visits tend to produce less clumped seed distributions (Graham et al. 1995). Also,avian frugivores often feed on the fruits of several plant species over short periods of time (Herrera 1984, 1988a; Levey et al. 1994) in some non-random pattern (Herrera 1998). This potentially produces a predictable spatial pattern of the dispersed seeds (White & Stiles 1990). Forest destruction leads to fragmentation and degradation of the remaining habitats, which may influence patterns of adult tree distribution if the production, predation, dispersal, and/or regeneration of tree seeds is affected (Harrington et al. 1997). If dispersal of avian frugivores is disrupted by habitat fragmentation, plant species might face reduced regeneration, or even local extinction if they depend on a single, locally extinct disperser (Kellman et al. 1996). Increased predation of seeds and regenerating plants in the edges and gaps may also directly reduce regeneration rates (Corlett & Turner 1997, Harrington et al. 1997, Schupp 1988).
A test of the hypothesis of ecological equivalence in an Australian subtropical rain forest
Authors: Penfold Guy C. , Lamb David
Published: August 2008

We tested the hypothesis that tree species in a subtropical rain forest in
south-east Queensland are ecologically equivalent and therefore have identical environmental
requirements for their regeneration. We assessed the evidence that juveniles of species differed
in their distributions in treefall gap microsites and along gradients of light availability,
soil pH, soil PO4-P availability and soil NO3-N availability. Pairwise comparisons were
made on a subset of the common species selected on the basis that they showed a relatively
high level of positive association, and would therefore, a priori, be expected to have similar
regeneration requirements. Detailed comparisons between the species failed to demonstrate
evidence for species differentiation with respect to their tolerance of the disturbance associated
with gap microsites or to the gradient of NO3-N availability. However, species differed
markedly in their distributions along the soil pH gradient and along the gradients of light
availability and soil PO4-P availability. The overall level of ecological differentiation
between the species is high: seven out of the 10 possible species pairings showed evidence for
ecological differentiation. Such niche differentiation amongst the juveniles of tree species
may play an important role in maintaining the species richness of rain-forest communities.
Seed rain beneath remnant trees in a slash-and-burn agricultural system in southern Cameroon
Authors: Carrière Stéphanie M. , André Mathieu , Letourmy Philippe , Olivier Isabelle , McKey Doyle B.
Published: August 2008

On clearing fields, Ntumu farmers in southern Cameroon leave some large trees. The seed rain beneath 30 such remnant trees (12 species) was compared with that 10 m away from the edges of their crowns. Of a total of 39 765 seeds recorded in 90 seed traps over 2 y, 73.6% were of species different from the tree associated with each set of traps (‘foreign seed rain’). Seed rain included 100 morphospecies, two-thirds of which possessed endozoochorous seeds. Seeds of the pioneer tree Musanga cecropioides accounted for 71.4% of total foreign seed rain; seeds of this and other animal-dispersed species accounted for 94.5% of the total. Seed rain was 25 times higher beneath remnant trees than 10 m away. Mean species richness of monthly seed rain was three times higher beneath remnant trees than 10 m away. Both fleshy-fruited and wind-dispersed species of remnant trees attracted seed-dispersing animals which greatly enhanced the seed rain; attraction thus did not depend solely on presence of fleshy fruits. Seed rain was lower when human activity in fields was intense and increased during the period of growth of the last crops, which were not usually weeded. Heavy seed rain just before fallow may contribute significantly to regeneration, as does the presence of remnant trees.
Effect of ingestion by bats and birds on seed germination of Stenocereus griseus and Subpilocereus repandus (Cactaceae)
Authors: Naranjo María Elena , Rengifo Carlos , Soriano Pascual J.
Published: August 2008

Effects of seed passage through digestive tracts of principal animal dispersers (bats and birds) on seed germination were investigated for two columnar cactus species, Stenocereus griseus and Subpilocereus repandus. In general, seeds ingested showed more rapid germination times and higher overall germination rates than untreated seeds. The bat Glossophaga longirostris, and the birds Mimus gilvus and Tachyphonus rufus seem to be the most efficient cacti dispersers in terms of quality of treatment. The increment of germination speed and particularly the decrease of imbibition time, could favour the probability of germination in dry areas such as arid and semi-arid environments.
Seed germination, seedling growth and habitat partitioning in two morphotypes of the tropical pioneer tree Trema micrantha in a seasonal forest in Panama
Authors: Silvera Katia , Skillman John B. , Dalling J. W.
Published: August 2008

We examined the distribution, germination, growth and photosynthetic characteristics of two co-existing morphotypes of the pioneer tree Trema micrantha at the Barro Colorado Nature Monument (BCNM), Panama. Morphotypes differed significantly in distribution and in seed characteristics. A ‘large’-seeded morphotype (endocarp mass=3.83 mg) was associated with treefall gaps in the forest interior, whereas a ‘small’-seeded morphotype (endocarp mass=1.38 mg) was found predominantly on landslides on the margins of Lake Gatun. Seeds of the small-seeded morphotype germinated faster than seeds of the large-seeded morphotype, with seedlings of the small-seeded morphotype showing both a higher Unit Leaf Rate (ULR) and a lower Specific Leaf Area (SLA). Differences in photosynthetic rates reflected differences in SLA; the small-seeded morphotype had a higher rate on a leaf area basis, while the large-seeded morphotype had a higher rate on a leaf mass basis. Although allocation patterns between morphotypes varied in a way consistent with known interspecific differences between ‘sun’ and ‘shade’ plants, relative growth rates (RGR) of the morphotypes were similar across different light conditions suggesting that factors other than light, such as water uptake efficiency, soil nutrient requirements, and perhaps seed dispersal characters may explain the habitat partitioning of morphotypes.
Rainfall but not selective logging affect changes in abundance of a tropical forest butterfly in Sabah, Borneo
Authors: Hill J. K. , Hamer K. C. , Dawood M. M. , Tangah J. , Chey V. K.
Published: August 2008

We investigated the effects of rainfall on the distribution and abundance of the satyrine butterfly Ragadia makuta in selectively logged and unlogged forest on Borneo. In 1997-98, there was a severe El Niño-Southern Oscillation (ENSO) drought, and annual surveys over a 4-y period showed that abundance of R. makuta was greatly reduced during the drought, but that populations quickly recovered after it. Monthly surveys over a 12-mo period of typical rainfall showed that high rainfall in the month preceding surveys significantly reduced butterfly abundance. Butterfly abundance and distribution did not differ between selectively logged and unlogged areas in either monthly or annual surveys and there was no difference between selectively logged and unlogged areas in the pattern of post-drought recovery. These results indicate that the abundance of R. makuta was significantly reduced both after high rainfall and during severe drought, but that these impacts were short-lived and were not affected by habitat disturbance. ENSO droughts on Borneo naturally often lead to widespread forest fires and thus impacts of ENSO events for butterflies are more likely to be due to indirect effects of habitat loss, rather than direct effects of drought on butterfly population dynamics.
Dispersal of Schinus fasciculatus seeds by the leaf-cutting ant Acromyrmex striatus in a shrubland of the dry Chaco, Argentina
Authors: Varela R. Omar , Perera Teresa C.
Published: August 2008

Ants are important agents of seed dispersal and they can
play a fundamental role in the establishment and survival
of plants (Beattie 1985). Leaf-cutting or fungus-growing
ants (Myrmicinae: Attini) are dominant elements of the
ant fauna throughout the neotropics. They collect different
types of vegetative and reproductive plant material that
serve as substrate for underground fungus gardens,which
are the only food source for their larvae (Stradling 1991).
Intraspecific variation in seed size affects scatterhoarding behaviour of an Australian tropical rain-forest rodent
Authors: Theimer Tad C.
Published: August 2008

Vertebrate seed dispersers could impact the evolution of seed size or alter the pattern of seedling recruitment if they responded differently to seeds of varying size (Jordano 1995). For example, models of seed caching by birds and mammals predict that seeds of higher nutritive value should be placed farther from parent trees and in lower densities than lower quality seeds (Clarkson et al. 1986, Stapanian & Smith 1978, Tamura et al. 1999). Comparisons of seed removal rates among tropical tree species in South-East Asia (Blate et al. 1998) and Australia (Osunkoya 1994) failed to show a relationship between seed size and removal rate, although the probability that a seed was scatterhoarded by
agoutis (Dasyprocta punctata) in a neotropical rain forest increased with interspecific seed size (Forget et al. 1998).
Reproductive biology of Montrichardia arborescens (Araceae) in French Guiana
Authors: Gibernau Marc , Barabé Denis , Labat Damien , Cerdan Philippe , Dejean Alain
Published: August 2008

Data on the pollination biology of neotropical aroids are still scarce and concern only a few species (Beath 1999, Croat 1997, Gibernau et al. 1999, 2000; Mayo et al. 1997 and references cited therein). It appears from these studies that Anthurium, Monstera and Spathiphyllum are on the whole pollinated mainly by bees (but see Kraemer & Schmitt 1999), whereas Dieffenbachia, Homalomena, Syngonium, Philodendron and Xanthosoma are generally beetle-pollinated. Although araceous inflorescences may be visited by several insect taxa (Madison 1979), only a few are the legitimate pollinators for each species (Seres & Ramirez 1995, Valerio 1984, Young 1986).
On Ringel duality for Schur algebras
Authors: ERDMANN KARIN , HENKE ANNE
Published: August 2008

In this paper we determine precisely the degrees r for which the Schur algebra
S(2, r) is its own Ringel dual.
Relations between the homologies of C*-algebras and their
commutative C*-subalgebras
Authors: LYKOVA ZINAIDA A.
Published: August 2008

The paper concerns the identification of projective closed ideals of C*-algebras.
We prove that, if a C*-algebra has the property that every closed left ideal is projective,
then the same is true for all its commutative C*-subalgebras. Further, we say a
Banach algebra A is hereditarily projective if every closed left ideal of A is projective.
As a corollary of the stated result we show that no infinite-dimensional AW*-algebra
is hereditarily projective. We also prove that, for a commutative C*-algebra A contained
in [Bscr ](H), where H is a separable Hilbert space, the following conditions are
equivalent: (i) A is separable; and (ii) the C*-tensor product A [otimes ]minA is hereditarily
projective. Howerever, there is a non-separable, hereditarily projective, commutative
C*-algebra A contained in [Bscr ](H), where H is a separable Hilbert space.
A Radon–Nikodým theorem for completely positive invariant
multilinear maps and its applications
Authors: HEO JAESEONG
Published: August 2008

Noncommutative Radon–Nikodým theorems have attracted a great deal of
attention in the theory of operator algebras. There has been considerable work on
non-commutative Radon–Nikodým theorems not only for C*-algebras but also for
algebras of unbounded operators [3, 5, 8, 9, 12, 13]. In this paper, we will develop
a Radon–Nikodým type theorem for completely bounded and completely positive
invariant multilinear maps.

The concept of matricial order has turned out to be very important to understand
the infinite-dimensional non-commutative structure of operator algebras. As
the natural ordering attached to this structure, completely positive maps and completely
bounded maps have been studied extensively. Results concerning completely
bounded maps have many applications: cohomology of operator algebras, multipliers
on group algebras, dilation theory, similarity theory, free product representations,
and abstract characterizations of operator algebras.
On lattices of continuous functions on a Stonian space
Authors: EDWARDS D. A.
Published: August 2008

Suppose that Ω is a compact Hausdorff space with a preorder [les ] whose graph is
closed, and let Ω∘ be an open subset of Ω. This paper provides conditions sufficient
to allow every increasing bounded real continuous function on Ω∘ to be extended
to an increasing real continuous function on Ω. These conditions are: (i) that Ω is a
Stonian space, and (ii) that the set C↑(Ω, [les ]) of increasing real continuous functions
on Ω is a regular Dedekind complete sublattice of C(Ω). Under these conditions it
is also shown that C↑(Ω, [les ]) is generated by idempotents, and an extension theorem
for idempotents is proved.
A distribution result for slices of sums of squares
Authors: CASTELLA FRANÇOIS , PLAGNE ALAIN
Published: August 2008

Asymptotically, the solutions of Waring’s problem follow a limit law of which we
are able to compute explicitly the limit density. In the special cases of sums of 3
and 4 squares where such a result is not possible, we establish a distribution result
for slices of at least h0(n) consecutive integers ending at n, that is integers from
n−h0(n)+1 to n, where h0(n) = nε for 4 squares and h0(n) = n¼+ε for 3 squares
(ε > 0). We then deduce from this study the asymptotic behaviour of some kind of
Riemann sums with an arithmetic constraint for which we point out an application
related to the study of Schrödinger equation.
Products in the mod 2 cohomology of certain split extensions of
cyclic by cyclic groups
Authors: HANDEL DAVID
Published: August 2008

Partial diagonal approximations are constructed for resolutions, due to Wall, of
certain split extensions of cyclic groups by cyclic groups of order 2. These are used
to determine the multiplicative structure in the cohomology of these groups arising
from certain coefficient pairings.
Homotopy classification of line fields and of Lorentz metrics on
closed manifolds
Authors: KOSCHORKE ULRICH
Published: August 2008

The problem of classifying line fields or, equivalently, Lorentz metrics up to
homotopy is studied. Complete solutions are obtained in many cases, e.g. for all closed
smooth manifolds N, orientable or not, of dimension n ≡ 0(4) and, in particular, in
the classical space-time dimension 4.

Our approach is based on the singularity method which allows us to classify the
monomorphisms u from a given (abstract) line bundle α over N into the tangent
bundle. The analysis of the transition to the image line field u(α) then centers around
the notion of ‘antipodality’.

We express our classification results in terms of standard (co-)homology and
characteristic classes. Moreover, we illustrate them for large families of concrete sample
manifolds by explicit bijections or by calculating the number of line fields.
Corrigendum and addendum to ‘asymptotic series for double zeta,
double gamma and Hecke L-functions’
Authors: MATSUMOTO KOHJI
Published: August 2008

Refined expressions are given for the error terms in the asymptotic expansion
formulas for double zeta and double gamma functions, proved in the author's former
paper [2]. Some inaccurate claims in [2] are corrected.
Asymmetric two-colourings of graphs in S3
Authors: FLAPAN ERICA , LI DAVID LINNAN
Published: August 2008

We prove that for any non-planar graph H, we can choose a two-colouring G of
H such that G is intrinsically chiral, and if H is 3-connected and is not K3,3 or K5,
then G is intrinsically asymmetric. No such asymmetric two-colouring is possible for
K3,3 or K5.
A new path integral representation for the solutions of the
Schrödinger, heat and stochastic Schrödinger equations
Authors: KOLOKOLTSOV VASSILI N.
Published: August 2008

Solutions to the Schrödinger, heat and stochastic Schrödinger equation with rather
general potentials are represented, both in x- and p-representations, as integrals over
the path space with respect to σ-finite measures. In the case of x-representation,
the corresponding measure is concentrated on the Cameron–Martin Hilbert space of
curves with L2-integrable derivatives. The case of the Schrödinger equation is treated
by means of a regularization based on the introduction of either complex times or
continuous non-demolition observations.
On amenability of the Banach algebras l∞(S, [Ufr ])
Authors: SÁNCHEZ FÉLIX CABELLO , GARCÍA RICARDO
Published: August 2008

Let [Ufr ] be an associative Banach algebra. Given a set S, we write l∞(S, [Ufr ]) for the
Banach algebra of all bounded functions f: S→[Ufr ] with the usual norm ∥f∥∞ =
sups∈S∥f(s)∥[Ufr ] and pointwise multiplication. When S is countable, we simply write
l∈([Ufr ]).

In this short note, we exhibit examples of amenable (resp. weakly amenable)
Banach algebras [Ufr ] for which l∈(S, [Ufr ]) fails to be amenable (resp. weakly amenable),
thus solving a problem raised by Gourdeau in [7] and [8]. We refer the reader to
[4, 9, 10] for background on amenability and weak amenability. For basic information
about the Arens product in the second dual of a Banach algebra the reader
can consult [5, 6].
Interpellation, Ideology and Identity: The Case of Talaq
Authors: Seet K. K.
Published: August 2008

The Singapore play, Talaq, was denied a public entertainment licence in October 2000 despite having been staged twice before, and its producer was arrested for trespassing when she refused to vacate the theatre in her bid to document the rehearsal process. The controversy, staged as a meta-drama by the print and broadcast media, reveals much about the cultural dynamics of Singapore's arts scene in respect of state subvention and artistic freedom, and the play itself raises questions about the performance of gender and ethnicity, as well as the political anatomy of the performing body.
The Dramatic Theatre in The Netherlands
Authors: Hildebrand Wil
Published: August 2008

An analysis of the main companies, groups and practitioners producing text-based theatre in the Netherlands in the last few years provides a backdrop for a more detailed examination of the work of writer/director Gerardjan Rijnders. Further, special focus is given to the work of the greatest theatre innovator of the last two decades, Jan Joris Lamers, and two young theatre collectives are presented as representative of a broader movement of playwrights, actors and directors, who perform in smaller black-box theatres.
The 1964 Civil Rights Act: Narrating the Past, Authorizing the Future
Authors: Hattam Victoria
Published: August 2008

Civil rights legislation of the sixties and seventies sought to end racial discrimination in the United States; doing so required that the federal government establish an official ethnoracial taxonomy in order to specify who was and was not covered by the various statutes. Specifically, the Civil Rights Act of 1964, the Voting Rights Act of 1965, the Fair Housing Act of 1968, the Equal Credit Opportunity Act of 1974, and the Home Mortgage Act of 1975 required federal agencies to identify particular groups to be monitored for evidence of discrimination. Since these statutes were enacted, scholars and activists have argued over their political effects. In fact, the questions raised are legion: Who has benefitted from civil rights protections? Has discrimination diminished or simply morphed into new forms? Who counts as a minority and on what grounds? How has the massive immigration of the last four decades intersected civil rights reform? Should foreign nationals qualify for civil rights protections? If yes, how do more recent claims to diversify fit with older notions that civil rights legislation as a means of redressing past wrongs?
Dominance effects as transderivational anti-faithfulness
Authors: Alderete John D.
Published: August 2008

This paper presents a theory of morphophonology based on a development in the
theory of faithfulness in Optimality Theory. A new constraint type,
anti-faithfulness, is proposed that evaluates a pair of related words and requires an
alternation in the shared stem. This constraint type is motivated initially by a set
of problems, e.g. morphological deletions, segmental exchanges and non-structure
preserving processes, which show that morphophonology must encompass more
than markedness–faithfulness interactions. The anti-faithfulness thesis is then
applied to accentual processes in which affixes idiosyncratically cause deletion of
accent in a neighbouring morpheme. It is argued that anti-faithfulness both
motivates the observed deletion and accounts for its properties with principles
that are generally available in phonological theory. Anti-faithfulness is then
shown to extend naturally to the analysis of other affix-induced alternations,
including accent insertions, shifts, and retractions of stress and tone, a result
which distinguishes this theory from plausible alternatives.
Principles applicable to the production of CALL-ware:
learning from the field of Human Computer Interaction (HCI)
Authors: ALLUM PAUL
Published: August 2008

To transform pedagogically sound classroom tasks into effective CALL-ware,
it is advantageous to have an approach that takes into account the general principles applicable
to all human computer interaction (HCI). This paper outlines an attempt at such an approach.
Teacher-designed, pedagogically sound software often fails in terms of usability, while highly usable,
professionally made software is often based on ideas that are not in accord with those of a particular
curriculum or teacher. The approach outlined below may assist in the process of transforming pedagogic
materials and practices already successfully used in the classroom into easily usable software.
Learner autonomy: a guiding principle in designing a CD-ROM for
intonation practice
Authors: KALTENBÖCK GUNTHER
Published: August 2008

Building on the experience of developing a CD-ROM for English intonation
practice, this article explores some advantages and limitations of this medium for the teaching of
suprasegmentals. Despite their undeniable potential for foreign language learning, computers prove to
be rather limited in their feedback to pronunciation, especially in terms of error identification and
correction, which calls into question one of their very strengths, viz. that of teacher-independent
learning. As a possible solution to this dilemma, the present paper proposes to build into the
design of a CD-ROM for intonation teaching the concept of learner autonomy, i.e. transferring to an
increased degree responsibility for the learning process from the teacher (computer) to the learner.
Drawing on the discussion of autonomy by, e.g. Broady & Kenning (1996) and Little (1999), it is
demonstrated how incorporating a metacognitive level (by offering the learner the choice to access
intonation in different ways) and a metalinguistic level helps to make the CD-ROM users more
autonomous in their learning and equip them with the necessary tools for self-assessment and
self-monitoring, which in turn can make up for the lack of computerised diagnostic feedback.
English learners’ dictionaries on CD-ROM as reference and language learning tools
Authors: WINKLER BIRGIT
Published: August 2008

This paper discusses the findings of two empirical studies which investigated
how students of English used two English learners’ dictionaries on CD-ROM. The outcome of these
studies will indicate in what way such dictionaries can serve as reference and language learning tools.
It is argued that an English learner’s dictionary on CD-ROM could be much more than an ‘ordinary’
reference work because it includes facilities that are not available in book form, such as audio and visual
elements, exercises and games. The studies suggest, however, that a number of changes in content and design
will have to be made in order to make such dictionaries more effective and beneficial to their users.
Learners, on the other hand, may need to acquire special skills in order to benefit from all the information
an English learner’s dictionary on CD-ROM contains.
A study on the effectiveness and usefulness
of Animated Graphical Annotation in Japanese CALL
Authors: HEW SOON-HIN , OHKI MITSURU
Published: August 2008

This paper describes an experiment in which an attempt was made to show that
Japanese Computer Assisted Language Learning (JCALL) with Animated Graphical Annotation (AGA) is
more effective and useful in assisting learners to acquire Japanese language listening skills
compared to JCALL without AGA. The independent variable in the experiment is AGA. The principal
research question addressed was, “Does the AGA used in the JCALL contribute to the students’
overall pronunciation and listening performances in elementary Japanese language courses by
looking into its AKUSENTO (symbol missing), SEION (symbol missing) and DAKUON (symbol missing) and TANON, CHOUON & SOKUON (symbol missing)?” The experiment was
conducted in Malaysia last summer. One hundred and twelve students (25 male and 87 female) who were
enrolled in Japanese language courses participated in this study. The students were randomly divided
into two groups and the pre-test/post-test approach was used in this study. The results of the
research showed AGA’s effectiveness in assisting the students to improve their listening skills.
However, AGA appeared to be less effective in helping the students to improve their
pronunciation skills.