bluuebunny/crossref_metadata_2025 huggingface dataset:
MDSF — A generic development and simulation facility for flexible, complex robotic systems
Authors: Ma Ou , Buhariwala Kerman , Roger Neil , MacLean John , Carr Robert
Published: July 2002

MDSF is a generic manipulator development and simulation facility developed by Spar Aerospace Limited, as a prime contractor to the Canadian Space Agency. It is an integral part of Canada's contribution to the International Space Station (ISS) program. MDSF is capable of simulating general robotic systems with complex and flexible structures undergoing all kinds of tasks including payload hand-over and contact with the environment. Rigorous validation and configuration control have been imposed throughout the development course of the simulation facility. Examples of current applications in the ISS program are included.
Optimal path planning of manipulatory systems subjected to
non-autonomous motion laws
Authors: Jutard-Malinge A. D. , Bessonnet G.
Published: July 2002

A path planning method is presented based on non-autonomous dynamic
modeling of open-loops in articulated systems. It is assumed that one part of
the mechanical system is submitted to specified motions laws, while movements of
the complementary part are free. Thus, motion optimization is related to free
joint movements but it is achieved on the basis of the dynamic model of the
whole mechanical system. This approach introduces a non-autonomous state
equation of a special type in the sense that it can not only depend on the
running time but also on the unknown travelling time. The cost function to be
minimized involves the travelling time and the actuating inputs. Optimization is
achieved by applying the Pontryagin Maximum Principle which yields a new
optimality condition concerning the travelling time dependency of the stated
problem. Two simulation examples are presented. The first one shows how the
developed technique makes possible both the reducing and mastering the dynamic
complexity of a four degrees of freedom-vertical manipulator. Set at four
degrees of freedom, the second one deals with a redundant planar manipulator
characterized by a mobile base that is submitted to a specified driving
motion.
Generation of robotic assembly sequences with consideration of line balancing using simulated annealing
Authors: Hong D.S. , Cho H.S.
Published: July 2002

An assembly sequence is considered to be optimal when the sequence
satisfies assembly constraints and yields the minimum assembly cost. While, a
line balancing solution is considered to be optimal when the solution has the
minimum idle time of the line, i.e. the minimum number of workstations for a
given cycle time. Although optimal assembly sequences are generated without
considering line balancing, they may not guarantee the minimum number of
workstations. In such case, additional cost should be required to accommodate
the increased number of workstations. Therefore, it is essential to consider
line balancing in the generation of cost-effective assembly sequences. To
generate such line-balanced assembly sequences for robotic assembly, this paper
treats a single-model and deterministic (SMD) assembly line balancing (ALB)
problem, and proposes a new method using a simulated annealing. In this method,
an energy function is derived in consideration of the satisfaction of assembly
constraints, and the minimization of assembly cost and the idle time. Then, the
energy function is iteratively minimized and occasionally perturbed by a
simulated annealing. When no further change in energy occurs, a solution of
assembly sequence with consideration of line balancing is finally obtained.
To show the effectiveness of the proposed scheme, case studies are presented
for industrial products such as an electrical relay and an automobile alternator.
Analysis of Impact in Robotic Peg-in-Hole Assembly
Authors: Liao Hsin-Te , Leu Ming C.
Published: July 2002

This paper presents an approach for analyzing the dynamics of initial impact during robotic parts mating represented by peg-in-hole assembly. Lagrange's impact model is used to derive a general form of impact equations for an industrial manipulator performing
peg-in-hole assembly. Specific impact equations can then be generated for a given robot to analyze part motions and contact forces in the mating of parts. The impact equations of a
SCARA robot are obtained and utilized to investigate how the system parameters affect force impulse and departure angle in the assembly of a peg with a chamfered hole. The resulting
information is useful to robot manufacturers in design of robotic equipment and to robot users in determining optimal operational conditions. It is also useful for building an intelligent robot controller capable of deciding on proper values of operation parameters.
Behaviour-based peg-in-hole
Authors: Pettinaro Giovanni C.
Published: July 2002

Given the high occurence rate in assembly industry, mating a peg into a hole can be considered as one of the most classic problem in robotics. Such a task has been extensively examined by many researchers who have repeatedly attempted to find out a general solution for it. Peg in hole, which is, needlessly to mention, extremely trivial for any human operator, is surprisingly difficult to have it carried out by a robot manipulator. The reason is partly due to a physical limitation of the mechanical compliance of the robot wrist and arm and partly to a lack of a mating strategy allowing the successful execution of the task whatever the initial position of peg and hole axes is. The work presented in this paper tackles a particular class of peg-in-hole (tandem peg-in-hole) and proposes within the behaviour-based paradigm a solution to its two main components (hole search and peg insertion) loosely modeled on the equivalent strategies performed by a blind human being in possess solely of the same sensing
capability (i.e. a simple differential touch sensor).
Teaching composing in secondary schools: the creative dream
Authors: Odam George
Published: July 2002

Composing is an obligatory activity at Key Stage 3 in the present National Curriculum in music for England and for Wales. The research programme, based on field visits, seminars and questionnaires, seeks to identify a basis for effective classroom practice through direct observation of experienced teachers and their pupils in twenty-six State secondary schools across England. Visits have also been made to Northern Ireland, Scotland and Wales. Group-work is the dominant working method in most secondary schools. Much time is at present wasted in group-work and it contributes significantly to stress in both teachers and pupils. Composing is largely an individual activity and this is insufficiently acknowledged or planned for at Key Stage 3. Too many teachers use methods inappropriate to the resources available to them. There are problems of progression and preservation of pupils' work. Despite these problems there is strong evidence that many children enjoy composing activities in school and compose music in and out of school for a variety of reasons and occasions. Composing is firmly established in our music education curriculum and provides a unique feature of practice in the United Kingdom. When composing is taught well, pupils look forward to their music lessons in the secondary school and approve of and enjoy composing activities.
Aesthetic education and the practice of music teaching
Authors: Plummeridge Charles
Published: July 2002

Over the past three decades it has become customary to regard music education as a form of aesthetic education. Recently a number of writers have expressed some objections to this view which they maintain has acquired the status of an accepted orthodoxy. In a healthy educational climate it is right that any orthodoxy should be questioned and aesthetic education has often become the subject of an international debate The purpose of this paper is not to add another voice to that debate but to re-examine the concept of aesthetic education with reference to the teaching and learning of music in educational institutions.

Many discussions on this issue become clouded because the term ‘aesthetic education’ is used in different ways and in different contexts In a broad sense the aesthetic is not necessarily associated with the arts and is taken to be a dimension of experience in any discipline; accordingly, aesthetic education is across the curriculum. Most frequently, it implies an education in the fine arts, the aim of which is the development in children of a particular style of thinking or mode of intelligence. A third view arises from the notion of aesthetics as a form of enquiry best described as the philosophy of art; aesthetic education thus conceived involves the study of topics such as artistic meanings, judgements and values.

An examination of these different conceptions of aesthetic education raises a number of philosophical and educational issues that have implications not only for the organisation and practice of music education in schools but also for the education and professional development of teachers.
HEALTH TECHNOLOGY ASSESSMENT IN THE NETHERLANDS
Authors: Bos Michael
Published: July 2002

The Dutch healthcare system is not a single overall

plan, but has evolved from a constantly changing mix of

institutions, regulations, and responsibilities. The

resulting system provides high-quality care with reasonable

efficiency and equal distribution over the population. Every

Dutch citizen is entitled to health care. Health insurance

is provided by a mix of compulsory national insurance and

public and private insurance schemes. Hospitals generally

have a private legal basis but are heavily regulated.

Supraregional planning of high-tech medical services is also

regulated. Hospitals function under fixed, prospective

budgets with regulation of capital investments. Independent

general practitioners serve a gatekeeper role for specialist

and hospital services and are paid by capitation or fee for

service. Specialists are paid by fee for service. All

physicians' fees are controlled by the Ministry of

Economic Affairs. Coverage of benefits is an important

method of controlling the cost of services. There is

increasing concern about health care quality. Health

technology assessment (HTA) has become increasingly visible

during the last 15 years. A special national fund for HTA,

set up in 1988, has led to many formal and informal changes.

HTA has evolved from a research activity into policy

research for improving health care on the national level. In

1993 the government stated formally that enhancing

effectiveness in health care was one of its prime targets

and that HTA would be a prime tool for this purpose. The

most important current issue is coordination of HTA

activities, which is now undertaken by a new platform

representing the important actors in health care and

HTA.
Fruiting phenology and seed dispersal syndromes in caatinga, a tropical dry forest in the northeast of Brazil
Authors: GRIZ LUCIANA MARIA SOBRAL , MACHADO ISABEL CRISTINA S.
Published: July 2002

This study describes the fruiting phenology of woody plants and their dispersal syndromes in caatinga
(semi-arid region in the northeast of Brazil). The fruiting phenology of 42 species with different dispersal modes and
life-forms was followed over a period of 1 y. Animal dispersal was the most commonly observed dispersal mode (36%),
followed by anemochory (33%), ballistic dispersal (19%) and barochory (12%). Overall, a greater number of species
fruited during the rainy season. Zoochorous species were the most representative in the rainy season, whereas
anemochorous species predominated during the dry season. Five different life-forms were observed, and the occurrence of
dispersal modes was discussed for each of them. In the caatinga plant community studied the patterns of life-forms,
fruiting phenology and seed dispersal syndromes were similar to other tropical seasonal ecosystems.

Este trabalho teve como objetivo principal descrever como se comportam as
espécies de caatinga (região semi-árida do Nordeste
brasileiro) com relação ao modo de dispersão durante as
estações seca e chuvosa. Foram observados também os
modos de dispersão apresentados em cada forma de vida. A fenofase de
frutificação foi acompanhada em 10 indivíduos de
42 espécies durante um intervalo de um ano. A zoocoria representou o
modo de dispersão mais observado (36%), seguido da anemocoria (33%),
balística (19%) e barocoria (12%). Um maior número de
espécies frutificou durante a estação de chuvas, sendo
a zoocoria mais representativa nesta estação, enquanto que a
anemocoria foi mais representativa na época de estiagem. Foram
observadas várias formas de vida, discutindo-se o modo de dispersão
em cada uma delas. Constatou-se que as espécies de caatinga estudadas
encontram-se dentro dos padrões gerais de época de dispersão
dos diásporos e representatividade das síndromes de dispersão
observados em outros ecossistemas com sazonalidade.
The densest terrestrial vertebrate
Authors: RODDA GORDON H. , PERRY GAD , RONDEAU RENÉE J. , LAZELL JAMES
Published: July 2002

An understanding of the abundance of organisms is central to understanding ecology, but many population density
estimates are unrepresentative because they were obtained from study areas chosen for the high abundance of the
target species. For example, from a pool of 1072 lizard density estimates that we compiled from the literature, we
sampled 303 estimates and scored each for its assessment of the degree to which the study site was representative.
Less than half (45%) indicated that the study area was chosen to be representative of the population or habitat. An
additional 15% reported that individual plots or transects were chosen randomly, but this often indicated only that the
sample points were located randomly within a study area chosen for its high abundance of the target species. The
remainder of the studies either gave no information or specified that the study area was chosen because the focal
species was locally abundant.
COMPARISONS OF DEPENDENCE FOR STATIONARY MARKOV PROCESSES
Authors: Hu Taizhong , Pan Xiaoming
Published: July 2002

Results and conditions which quantify the decrease
in dependence with lag for a stationary Markov process
and enable one to compare the dependence for two stationary
Markov processes are obtained. The notions of dependence
used in this article are the supermodular ordering and
the concordance ordering. Both discrete-time and continuous-time
Markov processes are considered. Some applications of the
main results are given. In queueing theory, the monotonicity
results of the waiting time of the nth customer
as well as the stationary waiting time in an MR/GI/1
queue and the stationary workload in a Markov-modulated queue
are established, thus strengthening previous results while
simplifying their derivation. This article is a continuation of
those by Fang et al. [7] and Hu and Joe [10].
On Ext2 between Weyl modules for quantum GLn
Authors: COX ANTON , ERDMANN KARIN
Published: July 2002

In the study of highest weight categories, the class of Weyl modules Δ(λ) and their
duals ∇(λ) are of central interest; this is for example motivated by the problem of
finding the characters of the simple modules. Weyl modules form the building blocks
for the category [Fscr ](Δ), whose objects have a filtration
0 = M0 [les ] M1 [les ] … [les ]
Mi−1 [les ] Mi = M
with quotients isomorphic to Δ(λ) for various λ. Knowing
Extr(Δ(λ), Δ(μ))
is essential for the understanding of this category.

In [3, 13], we determined Ext1 for Weyl modules
of SL(2, k) and q-GL(2, k) over
an infinite field k of characteristic p > 0.
Here we are able to extend these results to
determine Ext2 for Weyl modules in both these cases (see Theorem 4 · 6). Moreover,
this also gives Ext2 between any pair of Weyl modules
Δ(λ), Δ(μ) for q-GL(n, k)
(where n [ges ] 2) such that both λ and μ have at most two rows or two columns, or
where they differ by some multiple of a simple root (see Section 7).

Consider (for simplicity) polynomial representations of degree d
for GL(n, k). A
partition of d which has at most two rows is uniquely determined by the difference
in the row lengths, which we use as a label for the partition. In this case our main
result is
An algorithmic approach to knowledge evolution
Authors: LOMUSCIO ALESSIO , RYAN MARK
Published: July 2002

Intelligent agents must update their knowledge
base as they acquire new information about their environment.
The modal logic S5n has been designed for
representing knowledge bases in societies of agents. Halpern
and Vardi have proposed the notion of refinement of
S5n Kripke models in order to solve
multi-agent problems in which knowledge evolves. We argue that
there are some problems with their proposal and attempt to solve
them by moving from Kripke models to their corresponding
trees. We define refinement of a tree with a formula,
show some properties of the notion, and illustrate with the muddy
children puzzle. We show how some diagnosis problems in
engineering can be modelled as knowledge-based multi-agent
systems, and hence how our approach can address them.
A voxel-based representation for evolutionary shape optimization
Authors: BARON PETER , FISHER ROBERT , TUSON ANDREW , MILL FRANK , SHERLOCK ANDREW
Published: July 2002

A voxel-based shape representation when integrated
with an evolutionary algorithm offers a number of potential
advantages for shape optimization. Topology need not be
predefined, geometric constraints are easily imposed and,
with adequate resolution, any shape can be approximated
to arbitrary accuracy. However, lack of boundary smoothness,
length of chromosome, and inclusion of small holes in the
final shape have been stated as problems with this representation.
This paper describes two experiments performed in an attempt
to address some of these problems. First, a design problem
with only a small computational cost of evaluating candidate
shapes was used as a testbed for designing genetic operators
for this shape representation. Second, these operators
were refined for a design problem using a more costly finite
element evaluation. It was concluded that the voxel representation
can, with careful design of genetic operators, be useful
in shape optimization.
Seasonality and factors associated with cryptosporidiosis
among individuals with HIV infection
Authors: SORVILLO F. , BEALL G. , TURNER P. A. , BEER V. L. , KOVACS A. A. , KRAUS P. , MASTERS D. , KERNDT P. R.
Published: July 2002

The seasonality and factors associated with Cryptosporidium

infection were assessed in a cohort
of HIV-infected patients in Los Angeles County to better define the epidemiology
of
cryptosporidiosis among individuals with HIV. Data were analysed from a
cohort of 4247
patients [ges ]13 years of age with HIV infection enrolled from four outpatient
facilities in Los
Angeles, 1990–6. Cryptosporidiosis was diagnosed in 120 (2·8%)

patients. Among the 1296 individuals with complete follow-up until death,

cryptosporidiosis occurred in 69 (5·3%). The
seasonal rate of cryptosporidiosis showed a modest bimodal trend with the
highest rates
occurring in March–May and September–October. There
was no difference in the rate of
cryptosporidiosis for the periods of heaviest rainfall (December–March)
and low rainfall
(April–November). Infection rates were higher among males
(1·59 per 100 person-years) than
females (0·92) and lower in blacks (0·98) than other
racial/ethnic groups (1·80). A significant
trend of decreasing cryptosporidiosis was observed with increasing age,
with the highest rate
(2·34) in the 13–34 year age group. A strong association
between cryptosporidiosis and
CD4+ count was noted. These data suggest that cryptosporidiosis
among HIV-infected individuals in
Los Angeles County exhibits a modest spring and fall seasonality. This
pattern of occurrence
of cryptosporidiosis appears temporally unrelated to local rainfall patterns.
Our findings
suggest that HIV-infected men, individuals in younger age groups and those
with
CD4+ lymphocyte counts <100×106/l are at
increased risk of cryptosporidiosis. Blacks with HIV
infection appear less likely than other racial/ethnic groups to be
diagnosed with
Cryptosporidium infection. These results may provide insight into
possible routes of
transmission and sources of cryptosporidiosis infection in individuals
with HIV.
A serological survey of college students for antibody to
Cryptosporidium before and after the introduction of a new
water filtration plant
Authors: FROST F. J. , MULLER T. , CALDERON R. L. , CRAUN G. F.
Published: July 2002

In April 1997, a large city in the northeastern United States changed their drinking water
treatment practices. The city, which previously provided only chlorination for their surface
water sources added filtration in addition to chlorination. To assess whether Cryptosporidium
infections rates declined following filtration, we tested serological responses to 15/17-kDa and
27-kDa Cryptosporidium antigens among 107 community college students 1 month before and
225 students 5 months after filtration. Results suggest that levels of Cryptosporidium infections
did not decline following water filtration. However, seasonal changes in other exposures may
have confounded the findings. Swimming in a lake, stream or public pool and drinking
untreated water from a lake or stream predicted a more intense response to one or both
markers. Residence in the city, not drinking city tap water or drinking bottled water, gender,
travel or exposure to pets, young pets, diapers or a household child in day care were not found
to be predictive of more or less intense serological responses for either the 15/17-kDa and
27-kDa antigen.
Effect of monocular deprivation on NMDAR1 immunostaining
in ocular dominance columns of the marmoset Callithrix jacchus
Authors: FONTA CAROLINE , CHAPPERT CATHERINE , IMBERT MICHEL
Published: July 2002

We previously showed that immunoreactivity to N-Methyl-D-aspartate
(NMDA) receptors in primary visual cortex of Callithrix
jacchus is regulated by visual activity during the
second and third postnatal months (Fonta et al., 1997).
The purpose of the present study was to show that the columnar
pattern of high and low NMDAR1 immunoreactivity observed
in monocularly deprived animals corresponds to ocular dominance
columns linked to the nondeprived and deprived eye, respectively.
We compared cortical distribution of NMDAR1 receptors and
the projection zones of thalamic afferents, revealed by
transneuronal transport of tritiated proline, in 2-month-old,
either monocularly deprived or control, marmosets. The
data show that ocular dominance columns exist in 2-month-old
marmosets and that a 2-week monocular deprivation by means
of eyelid suture leads to a modification of the thalamo-cortical
afferents organization. Experiments of neuronal tracing
and immunohistochemistry performed on the same animals
demonstrated that cortical domains with decreased NMDAR1
level correspond to the deprived eye columns. These investigations,
coupled to the previous results, strongly suggest that
the NMDA receptors, regulated by visual activity, are involved
in the refining of ocular dominance columns in the primary
visual cortex of juvenile marmoset.
Corticostriatal and corticotectal neurons in area 6 of the
cat during fixation and eye movements
Authors: WEYAND THEODORE G. , GAFKA ADELE C.
Published: July 2002

We studied the visuomotor properties of 54 corticostriatal
(CS) and 38 corticotectal (CT) neurons in a region of area
6 that largely corresponds to the cat's frontal eye
fields in five cats trained to do simple oculomotor tasks.
Overall, these cells were similar to the general population
of area 6 neurons described in the previous paper (Weyand
& Gafka, 1998), with very few showing pre-saccadic
activity. Likewise, CS and CT cells were similar to each
other, although only CS cells showed activity exclusively
related to the delivery of the reward and CT cells were
more likely to be active during saccades. Variability in
visual response latencies and the observation that some
cells showed initial visual suppression suggest CS and
CT cells reflect the output of a variety of intracortical
circuits. Despite similar response properties and overlapping
laminar origin, CS and CT circuits appear largely independent.
Among 32 cells that we could electrically activate (either
synaptically or antidromically) from the superior colliculus,
only two could also be activated from stimulating electrodes
in the striatum. Similarly, 23 of 25 cells electrically
activated from the striatum could not be activated from
the superior colliculus. Although few of these efferent
cells exhibited pre-motor activity, many exhibit properties
that could contribute to gaze control.
Spectral and polarization sensitivity of photocurrents of
amphibian rods in the visible and ultraviolet
Authors: PALACIOS ADRIAN G. , SRIVASTAVA RANJANA , GOLDSMITH TIMOTHY H.
Published: July 2002

Photocurrents from isolated rods of adults and
sub-adults of three species of amphibians, Rana pipiens,
Ambystoma tigrinum, and Xenopus laevis,
were measured with suction pipette electrodes. The intensity
for a half-maximal response was 0.91 ± 0.48 photons
μm−2 flash−1 (mean
± s.d., 10-ms flashes) for Rana,
0.92 ± 0.44 for Ambystoma, and 6.14 ±
1.33 for Xenopus. The mean number of photoisomerizations
at half-saturation was 22 ± 12 for Rana,
50 ± 24 for Ambystoma, and 221 ±
48 for Xenopus. The photocurrent per photoisomerization
is several times smaller in Xenopus rods than
in the other two species. Spectral sensitivity was measured
from 277–737 nm with light polarized both parallel
and perpendicular to the planes of the membrane disks.
Dichroism fell in the near UV and was absent in the region
of absorption by tryptophan and tyrosine. Maximum sensitivity
of Rana was at 503.9 ± 2.6 nm (n
= 86), and of Ambystoma, 505.8 ± 1.8 nm
(n = 24). Animals from these same batches that
were sampled by HPLC had no 3-dehydroretinal (retinal2).
Xenopus containing about 94% retinal2
and 6% retinal1 had λmax
at 519.3 ± 2.7 nm (n = 11). Spectral position
of the β-band, estimated by the method of Stavenga
et al. (1993), appears to be at longer wavelengths in amphibian
photoreceptors than in other vertebrates. Fits of log sensitivity
to a normalized-frequency template that tracks the long-wavelength
tail of the α-band (Lamb, 1995) show that the rod pigments
of Rana and Ambystoma are slightly narrower
than those found in the photoreceptors of fish and mammals.
The influence of fixational eye movements on the response
of neurons in area MT of the macaque
Authors: BAIR WYETH , O'KEEFE LAWRENCE P.
Published: July 2002

We analyzed the relationship between eye movements
and neuronal responses recorded from area MT in alert monkeys
trained to maintain visual fixation during the presentation
of moving patterns. The monkeys made small saccades which
moved the eyes with velocities that spanned the sensitivity
range of MT neurons. The saccades evoked changes in the
neuronal response that depended upon (1) the level of stimulus-evoked
activity amidst which the saccade occurred and (2) the
direction of the saccade relative to the preferred direction
of the neuron. Most notably, saccades were able to suppress
stimulus-evoked activity when they caused retinal image
flow that opposed the neuron's preference and were
able to elicit a response or enhance weak activity when
they caused flow in the neuron's preferred direction.
On average, the disturbance lasted 40 ms beginning about
40 ms following saccade onset. Using these parameters,
we simulated synthetic spike trains from an imaginary pair
of similarly tuned neurons and determined that the interneuronal
correlation due to saccades should be negligible at all
but the lowest ongoing firing rates. This conclusion was
supported from our data by the observation that response
variance for single MT spike trains was not measurably
reduced during periods of stable gaze compared to periods
when eye movement exceeded a stability criterion (0.1 deg
during 0.5 s). While the intrusions caused by saccades
are too short-lived and infrequent to account for the variability
of MT neuronal response (counter to the finding in V1 of
Gur et al., 1997), the clear directional signal that they
carry in area MT suggests that motion perception is not
blocked during saccades by suppression at early stages
in the visual pathway.
Peripheral shift reduces visual sensitivity in cat geniculate
neurones
Authors: DERRINGTON ANDREW M. , FELISBERTI FATIMA
Published: July 2002

The sudden displacement of the retinal image during
a saccade raises the visual threshold of human observers
to foveal stimuli. The fall in visual sensitivity observed
during this phenomenon, known as saccadic suppression,
seems to occur very early in the visual processing chain.
The lateral geniculate nucleus (LGN) is a likely locus
for the multiple retinal and extraretinal interactions
occurring during saccadic eye movements, therefore we used
the responses of relay cells of adult cats to simulate
a pychophysical experiment. We first measured the responses
of X and Y relay cells (27 X and 13 Y) to central spots
of optimal size and different contrasts. The spots were
presented either alone or time locked with the rapid movement
of a large, high-contrast peripheral pattern, referred
to as shift. We measured the percentage of trials
on which the relay cell fired more spikes when the spot
(contrast: 0.03–1.0) was present than when it was
absent. In experiments with human observers the task was
to indicate, by a keypress, which of two otherwise identical
temporal intervals contained the spot. The shift reduces
the sensitivity (raises the contrast threshold) of neurones
in the cat relay cells to brief, stationary targets presented
to the receptive-field center. The suppression of visual
sensitivity is significantly greater in Y cells than in
X cells (average sensitivity ratios 5.6 ± 5.4 in
Y cells, 1.59 ± 0.9 in X cells: P <
0.001, U test). The shift also reduces the sensitivity
of human observers to the same target. This suggests that
the LGN is a potential locus for the modulation of visual
responses that leads to saccadic suppression.
Opiate and N-methyl-D-aspartate receptors in form-deprivation
myopia
Authors: FISCHER ANDY J. , SELTNER RUTH L.P. , STELL WILLIAM K.
Published: July 2002

Pharmacological studies have implicated retinal
opiate pathways in the visual regulation of ocular growth.
However, the effects of opiate receptor subtype-specific
compounds on form-deprivation myopia (FDM) are inconsistent
(Seltner et al., 1997), and may be mediated by non-opiate
receptors. The purpose of this study was to test whether
opiate receptor-inactive (D-) enantiomers elicit
the same FDM-suppressing effect as their opiate receptor-active
(L-) counterparts. Since some opiates are thought
to act at NMDA receptors, we also tested whether NMDA receptor
agonists and antagonists influence ocular growth or FDM.
We found that both L- and D- enantiomers
of morphine-like compounds (dextrorphanol and levorphanol,
and D- and L-naloxone) were equally effective
in blocking FDM. The NMDA receptor antagonists dextromethorphan,
MK801, and AP5 also suppressed FDM. A single toxic dose
of NMDA, that destroys many subtypes of amacrine cells
(including those that synthesize the opioid peptide enkephalin),
induced myopia and ocular enlargement in ungoggled eyes,
and eliminated the ability of form-deprivation to enhance
ocular growth. The NR-1 subunit of the NMDA receptor was
localized to a narrowly stratified, intense stratum at
approximately 50% depth in the inner plexiform layer, diffusely
throughout the proximal inner plexiform layer, and to many
somata in the amacrine and ganglion cell layers. These
observations suggest that most effects of opiate receptor
ligands on FDM in the chick are mediated by non-opiate
receptors, which are likely to include NMDA receptors.
NMDA as an excitotoxin transiently enhances ocular growth,
but thereafter disables retinal mechanisms that promote
emmetropization and FDM. These observations are consistent
with a prominent role for pathways utilizing NMDA receptors
in FDM and ocular growth-control.
Neural correlates of boundary perception
Authors: LEVENTHAL AUDIE G. , WANG YONGCHANG , SCHMOLESKY MATTHEW T. , ZHOU YIFENG
Published: July 2002

The responses of neurons in areas V1 (17) and V2
(18) of anesthetized and paralyzed rhesus monkeys and cats
were recorded while presenting a set of computer-generated
visual stimuli that varied in pattern, texture, luminance,
and contrast. We find that a class of extrastriate cortical
cells in cats and monkeys can signal the presence of boundaries
regardless of the cue or cues that define the boundaries.
These cue-invariant (CI) cells were rare in area V1 but
easily found in V2. CI cortical cells responded more strongly
to more salient boundaries regardless of the cue defining
the boundaries. Many CI cortical cells responded to illusory
contours and exhibited the same degree of orientation and
direction selectivity when tested with boundaries defined
by different cues. These cells have significant computational
power inherent in their receptive fields since they were
able to generalize across stimuli and integrate multiple
cues simultaneously in order to signal boundaries. Cells
in higher order cortical areas such as MT (Albright, 1992),
MST (Geesaman & Anderson, 1996), and IT (Sary et al.,
1993) have previously been reported to respond in a cue
invariant fashion. The present results suggest that the
ability to respond to boundaries in a cue-invariant manner
originates at relatively early stages of cortical processing.
Analysis of dendritic arbors of native and regenerated ganglion
cells in the goldfish retina
Authors: CAMERON DAVID A. , VAFAI HOUMAN , WHITE JOHN A.
Published: July 2002

The retinas of adult teleost fish can regenerate
following injury, but little is known about the neuronal
integration of the visual scene that is performed by the
regenerated retina. Using goldfish retinal ganglion cells
(RGCs) as the experimental system, an evaluation of dendritic
arbor structure and passive electrotonic properties was
developed, the aim being to quantitatively test the hypothesis
that native and regenerated RGC dendritic arbors have similar
structural and modeled electrotonic attributes. Fractal
dimension was chosen as the descriptor of RGC dendritic
arbor complexity, and the arbors' transfer function
magnitudes were estimated using an electrically passive,
equivalent-circuit analysis. For both native and regenerated
RGCs, arbors qualitatively judged to be simple tended to
have lower fractal dimension values than arbors judged
to be more complex. All cells had similar cut-off frequencies,
and for random stimulation of greater than 25% of an RGC's
population of dendritic tips, there was a positive correlation
between fractal dimension and transfer function magnitude.
Some regenerated RGCs had abnormally long primary dendrites,
but neither the distributions of fractal dimension values,
nor the estimated transfer function magnitudes, were significantly
different between native and regenerated RGCs. The results
appear to support the hypothesis that structural and modeled
electrotonic attributes of regenerated goldfish RGCs are
similar to those of native RGCs, suggesting that regenerated
RGCs may restore normal visual function.
Sustained and transient oscillatory responses in the gamma
and beta bands in a visual short-term memory task in humans
Authors: TALLON-BAUDRY CATHERINE , KREITER ANDREAS , BERTRAND OLIVIER
Published: July 2002

In a visual delayed matching-to-sample task, compared
to a control condition, we had previously identified different
components of the human EEG that could reflect the rehearsal
of an object representation in short-term memory (Tallon-Baudry
et al., 1998). These components were induced oscillatory
activities in the gamma (24–60 Hz) and beta (15–20
Hz) bands, peaking during the delay at occipital and frontal
electrodes, and two negativities in the evoked potentials.
Sustained activities (lasting until the end of the delay)
are more likely to reflect the continuous rehearsing process
in memory than transient (ending before the end of the
delay) activities. Nevertheless, since the delay duration
we used in our previous experiment was fixed and rather
short, it was difficult to discriminate between sustained
and transient components. Here we used the same delayed
matching-to-sample task, but with variable delay durations.
The same oscillatory components in the gamma and beta bands
were observed again during the delay. The only components
that showed a sustained time course compatible with a memory
rehearsing process were the occipital gamma and frontal
beta induced activities. These two activities slowly decreased
with increasing delay duration, while the performance of
the subjects decreased in parallel. No sustained response
could be found in the evoked potentials. These results
support the hypothesis that objects representations in
visual short-term memory consist of oscillating synchronized
cell assemblies.
Home‐range use by the tufted capuchin monkey (Cebus apella nigritus) in a subtropical rainforest of Argentina
Authors: Di Bitetti Mario S.
Published: July 2002

The pattern of home‐range use by seven groups of tufted capuchin monkeys Cebus apella nigritus is described in the Iguazú National Park, Argentina, during 1991–94. The seasonal changes in home‐range use by one of these groups between August 1997 and December 1998, are correlated with changes in food distribution and availability. Fruit availability was estimated with fruit traps, and the abundance and distribution of food was experimentally changed within the home range of one group by using feeding platforms filled with bananas. Average home‐range size is 161 ± 77 ha (range = 81–293 ha, n= 7). There is a positive relationship between the number of females per group and home‐range size. Neighbouring groups have partially overlapping home ranges and aggressive relationships. Fruit abundance is scarce during the winter and peaks during the spring and early summer. The pattern of home‐range use by the main study group of capuchins was consistent with the hypothesis that fruit distribution and availability is the most important factor affecting the spatial use of their range. This is evidenced by the changes in range size and in range use as the distribution and abundance of their main fruit sources change seasonally. Range use shifted dramatically during the experimental phase of this study; the capuchins reduced their range and most frequently visited the areas where the feeding platforms were located. For most populations of frugivorous monkeys, fruit distribution and availability are the main factors that determine the pattern of home‐range use. However, in some populations the availability of water sources and sleeping sites can have some effect on range use. For capuchin monkeys in particular, within‐species variation in home‐range size, degree of range overlap and interactions between neighbouring groups are large and do not serve to characterize any species of Cebus monkeys.
Diets for fat sets
Authors: ERWIG MARTIN
Published: July 2002

In this paper we describe the discrete interval encoding tree
for storing subsets of
types having a total order and a predecessor and a successor function. In the
following, we consider for simplicity only the case for integer sets; the generalization
is not difficult.

The discrete interval encoding tree is based on the observation that the set of
integers {i[mid ]a[les ]i[les ]b}
can be perfectly represented by the closed interval [a, b].
The general idea is to represent a set by a binary search tree of integers in which
maximal adjacent subsets are each represented by an interval. For example, inserting
the sequence of numbers 6, 9, 2, 13, 8, 14, 10, 7, 5 into a binary search tree, respectively,
into a discrete interval encoding tree results in the tree structures shown in figure 1.

The efficiency of the interval representation, both in terms of space and time,
improves with the density of the set, i.e. with the number of adjacencies between set
elements. So what we propose is a ‘diet’ (discrete interval encoding tree)
for ‘fat’ sets in the sense of ‘the same amount of information
with less nodes’.
Can computerised testing be authentic?
Authors: LAURIER MICHEL
Published: July 2002

The concept of authenticity first appeared with the development of the
communicative approach. More recently, in the field of educational measurement, authentic
assessment methods have been proposed. Although adaptive testing seems to be the most important
application of computers in language assessment, these tests are usually not authentic.
Since many real world tasks are accomplished with computers, these may be used for authentic direct
testing. Computers may be also used in semi-direct testing as a way to enhance the context. Finally
in authentic assessment, computers may be used as a tool to process the data when the learners
use them to organise their portfolio. Using the computer, test developers can also create
better authentic tests.
Physical therapy to improve movement performance and functional ability poststroke.
Part 2. A research direction.
Authors: Pomeroy VM , Tallis RC
Published: July 2002

Introduction

Physical therapy forms a large part of the multi-professional package of stroke
care which has been shown to save lives and reduce disability, effects
which may be maintained in the longer term. More specifically, physical
therapy may improve performance of movement and functional ability poststroke, especially
in the form of exercise-based interventions, and increased
intensity of physical therapy may bring increased benefit. However,
there is little evidence on which to base clinical decisions about what interventions
to give to which patients, in what intensity and at what stage in the recovery process.
In short, much of physical therapy practice remains based on clinical belief rather
than objective evidence and robust research is needed.
Mitochondrial damage in human aging
Authors: Brierley Elizabeth J
Published: July 2002

Introduction

Aging is a detrimental, progressive process that affects all human beings fortunate to live long enough. This indistinct process renders an individual increasingly susceptible to disease, disability and death. For this reason, aging is expensive, both personally for an individual and financially for society as a whole. Aging is probably the result of damage to several different mechanisms. There are numerous potential contenders, one of which is the involvement of mitochondria. Harman in 1972 was one of the first to suggest that mitochondria may have a central role in aging. Linnane in 1989 proposed that the accumulation of mitochondrial DNA (mtDNA) mutations during life is a major cause of age-related disease. With the explosion of molecular biology in the last decade, our understanding of mitochondrial aging has advanced, raising many questions as to if and how mtDNA mutations may be involved in aging.
Discovery of manuscripts on Gramineae and Cyperaceae by C. G. Nees von Esenbeck
Authors: Editor Journal
Published: July 2002

..
Critical Notice: Why Killing Is Not Always Worse—and
Is Sometimes Better—Than Letting Die
Authors: KUHSE HELGA
Published: July 2002

The philosophical debate over the moral difference
between killing and letting die has obvious relevance for
the contemporary public debate over voluntary euthanasia.
Winston Nesbitt claims to have shown that killing someone
is, other things being equal, always worse than allowing
someone to die. But this conclusion is illegitimate.
While Nesbitt is correct when he suggests that killing
is sometimes worse than letting die, this is not
always the case. In this article, I argue that there are
occasions when it is better to kill than to let die.
Response to “Neonatal Viability in the 1990s: Held
Hostage by Technology” by Jonathan Muraskas et al.
and “Giving ‘Moral Distress’ a Voice:
Ethical Concerns among Neonatal Intensive Care Unit Personnel”
by Pam Hefferman and Steve Heilig (CQ Vol 8, No 2)
Authors: Simpson Thomas J.
Published: July 2002

Muraskas et al. and Hefferman and Heilig present the
painfully elusive ethical questions regarding decisionmaking
in the care of the extremely low birth weight (ELBW) infants
in the intensive care nursery. At what gestation or size
do we resuscitate? Can we stop resuscitation after we have
started? How much money is too much to spend? Is the distress
of the parents of the ELBW infant, the anguish of their
caregivers, and the moral and ethical uncertainty of the
approach to these infants too much to pay? Who speaks for
the neonate: the parent, nurse, attorney, or physician?
Ideally these questions should have been answered 30 years
ago when modern neonatology embarked on a journey from
where it could not return. A new breed of physician, called
“neonatologist,” seduced by the high-tech lure
and the promise of saving lives previously unsavable pioneered
a lucrative and life-saving technological revolution in
the care of premature newborns. This rapid advancement
in neonatology occurred a few years after the death of
a premature infant named Patrick Kennedy in 1963. While
the country mourned, medical scientists vowed that this
would not happen again. First continuous positive airway
pressure, then mechanical ventilation, changed medical
care of premature newborns forever. It began an era of
euphoria and excitement. Neonatologists raced to push to
the edge of newborn viability. What was the youngest salvageable
gestational age? What was the smallest that could be saved?
Yes, we dreamed, and still do dream of artificial placentas.
Ethical questions took a back seat in the search for the edge because the waters were uncharted and the tough questions could not be answered without experience. What was to be the cost in dollars and in anguish to save the Patrick Kennedys of the world? Triumphs led to grave concerns as we approached the edge. However, no advancement in neonatology has ever changed the ultimate questions.
Fast Unimodular Counting
Authors: MOUNT JOHN
Published: July 2002

This paper describes methods for counting the number of nonnegative integer solutions of
the system Ax = b when A is a nonnegative
totally unimodular matrix and b an integral
vector of fixed dimension. The complexity (under a unit cost arithmetic model) is strong
in the sense that it depends only on the dimensions of A and not on the size of the entries
of b. For the special case of ‘contingency tables’
the run-time is 2O(√dlogd) (where d is
the dimension of the polytope). The method is complementary to Barvinok's in that our
algorithm is effective on problems of high dimension with a fixed number of (non-sign)
constraints, whereas Barvinok's algorithms are effective on problems of low dimension and
an arbitrary number of constraints.
Self-Similarity Bounds for Locally Thin Set Families
Authors: FACHINI EMANUELA , KÖRNER JÁNOS , MONTI ANGELO
Published: July 2002

A family of subsets of an n-set is k-locally thin if, for every k-tuple of its members, the
ground set has at least one element contained in exactly one of them. For k = 5 we derive a
new exponential upper bound for the maximum size of these families. This implies the same
bound for all odd values of k > 3. Our proof uses the graph entropy bounding technique to
exploit a self-similarity in the structure of the hypergraph associated with such set families.
List Improper Colourings of Planar Graphs
Authors: šKREKOVSKI R.
Published: July 2002

A graph G is m-choosable with impropriety d,
or simply (m, d)*-choosable, if for every
list assignment L, where [mid ]L(v)[mid ][ges ]m
for every v∈V(G), there exists an L-colouring of
G such that each vertex of G has at most d neighbours
coloured with the same colour as
itself. We show that every planar graph is (3, 2)*-choosable and every outerplanar graph is
(2, 2)*-choosable. We also propose some interesting problems about this colouring.