Image-matching during ant navigation occurs through saccade-like body turns controlled by learned visual features

Visual memories of landmarks play a major role in guiding the habitual foraging routes of ants and bees, but how these memories engage visuo-motor control systems during guidance is poorly understood. We approach this problem through a study of image matching, a navigational strategy in which insects reach a familiar place by moving so that their current retinal image transforms to match a memorized snapshot of the scene viewed from that place. Analysis of how navigating wood ants correct their course when close to a goal reveals a significant part of the mechanism underlying this transformation. Ants followed a short route to an inconspicuous feeder positioned at a fixed distance from a vertical luminance edge. They responded to an unexpected jump of the edge by turning to face the new feeder position specified by the edge. Importantly, the initial speed of the turn increased linearly with the turn's amplitude. This correlation implies that the ants' turns are driven initially by their prior calculation of the angular difference between the current retinal position of the edge and its desired position in their memorized view. Similar turns keep ants to their path during unperturbed routes. The neural circuitry mediating image-matching is thus concerned not only with the storage of views, but also with making exact comparisons between the retinal positions of a visual feature in a memorized view and of the same feature in the current retinal image.

Life expectancy free of disability: a composite measure of population health status

Access to disability data from a nationwide survey of New Zealanders provides the opportunity to estimate Life Expectancy Free of Disability (LEFD) for the non-institutional adult population. This measure of population health status combines mortality and morbidity data into a single index. The analysis is restricted to the 15-64 age range and results on partial life expectancy free of disability are presented for the key sociodemographic groups. The results conform to the international evidence and highlight the potential impact of disability as a component in a composite measure of population health status: although women live longer than men, almost all this apparent advantage in longevity is spent in some state of disablement; Maori are disadvantaged in comparison with non-Maori both in terms of longevity and in the proportion of the life span spent disability-free; and, social class comparisons show a decline in LEFD with declining social class that is steeper than the corresponding mortality gradient. Despite some technical difficulties and the strong requirements of the data, the LEFD measure has many potential applications in public health research and planning. In particular, it has the potential to direct research and policy towards the enhancement of the active years of life rather than just the postponement of mortality.

What can be learnt from analysing insect orientation flights using probabilistic SLAM?

In this paper, we provide an analysis of orientation flights in bumblebees, employing a novel technique based on simultaneous localisation and mapping (SLAM) a probabilistic approach from autonomous robotics. We use SLAM to determine what bumblebees might learn about the locations of objects in the world through the arcing behaviours that are typical of these flights. Our results indicate that while the bees are clearly influenced by the presence of a conspicuous landmark, there is little evidence that they structure their flights to specifically learn about the position of the landmark.

Standards-based network monitoring for the grid

As large grid infrastructures, such as Enabling Grids for E-sciencE, mature, they are being used by scientists around the world in their daily work, running thousands of concurrent computational jobs and transferring large amounts of data. The successful and sustainable operation of such grid infrastructures is only possible through the use of monitoring tools. The underlying networks upon which grid infrastructures are built are critical to their operation; therefore, network monitoring becomes an important part of the overall grid monitoring strategy. In this paper, the design and implementation of a set of tools for providing access to federated network monitoring data are presented, based on standards developed within the Open Grid Forum Network Measurements Working Group (NM-WG). These tools give access to data collected by heterogeneous, NM-WG compliant network monitoring tools.

"This is a kind of betrayal": a qualitative study of disability after breast cancer

OBJECTIVE

We proposed to document the effect of arm morbidity and disability in 40 Canadian women who were 12-24 months post breast cancer surgery.

METHODS

We completed 40 qualitative interviews as one component of a multidisciplinary national longitudinal study of arm morbidity after breast cancer (n = 745) involving four research sites (Fredericton/Saint John, Montreal, Winnipeg, Surrey). During semi-structured interviews, participants who had reported arm morbidity and disability in earlier surveys were asked to discuss the effects of these conditions on everyday life.

RESULTS

The interviewees reported making major adjustments to paid and unpaid work, which often involved the assistance of family members, thus demonstrating the effect of disability. Interview data resulted in the creation of a model that addresses arm morbidity and disability, and that holds implications for health care professionals.

CONCLUSIONS

Based on the interview findings, we conclude that a robust measure of disability after breast cancer should be developed. In the absence of a validated measure of the effect of disability, evaluating qualitative responses to questions about everyday activities could provide the impetus for provision of physical therapy and emotional support.

Accrediting radiation technique in a multicentre trial of chemoradiation for pancreatic cancer

Before a multicentre trial of 3-D conformal radiotherapy to treat cancer of the pancreas, participating clinicians were asked to complete an accreditation exercise. This involved planning two test cases according to the study protocol, then returning hard copies of the plans and dosimetric data for review. Any radiation technique that achieved the specified constraints was allowed. Eighteen treatment plans were assessed. Seven plans were prescribed incorrect doses and two of the planning target volumes did not comply with protocol guidelines. All plans met predefined normal tissue dose constraints. The identified errors were attributable to unforeseen ambiguities in protocol documentation. They were addressed by feedback and corresponding amendments to protocol documentation. Summary radiobiological measures including total weighted normal tissue equivalent uniform dose varied significantly between centres. This accreditation exercise successfully identified significant potential sources of protocol violations, which were then easily corrected. We believe that this process should be applied to all clinical trials involving radiotherapy. Due to the limitations of data analysis with hard-copy information only, it is recommended that complete planning datasets from treatment-planning systems be collected through a digital submission process.

Soft x-ray measurements using photoconductive type-IIa and single-crystal chemical vapor deposited diamond detectors

Photoconductive detectors (PCDs) are routinely used alongside vacuum x-ray diodes (XRDs) to provide an alternative x-ray flux measurement at laser facilities such as HELEN at AWE Aldermaston, UK, and Omega at the Laboratory for Laser Energetics. To evaluate diamond PCDs as an alternative to XRD arrays, calibration measurements made at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory are used to accurately calculate the x-ray flux from a laser-heated target. This is compared to a flux measurement using the Dante XRD diagnostic. Estimates indicate that the photoinduced conductivity from measurements made at Omega are too large, and calculations using the radiometric calibrations made at the NSLS agree with this hypothesis. High-purity, single-crystal, chemical vapor deposited (CVD) diamond samples are compared to natural type-IIa PCDs and show promising high resistivity effects, the corollary of which preliminary results show is a slower response time.

The effect of hypotonicity on the mean platelet volume of patients with thrombo-embolism

When dipotassium EDTA anticoagulated platelet rich plasma was incubated against a range of hypotonic saline concentrations, platelet volume was seen to change in a particular and reproducible fashion. When platelets taken from patients suffering a thromboembolic episode were tested in the same manner, a different pattern of response was observed the platelets being far less tolerant to osmotic stress. Similar changes occurred in platelets from ante-natal subjects. Platelets from both groups regained their tolerance to hypotonicity following either the thromboembolic incident or parturition respectively.

Temperament: a consideration of concepts and methods

This paper discusses conceptual issues and begins with a consideration of definitions of temperament. It is suggested that the purposes for which temperament has been studied have, to some degree, dictated methods used and inferences drawn. Those psychopathologists interested in the relationship between temperament and psychiatric disorder, or emotional and behavioural disturbance, have tended to use different methods from those more concerned with delineating the structure of personality. Some issues and problems are common to both approaches, e.g. the definition of behaviour reflecting temperament in terms of style rather than content. Other issues, such as the difficulty involved in drawing a clear distinction between temperamental attributes and mental disorders, are restricted to one approach. The relative contribution of gentic and environmental effects is of interest to both psychopathologists (who wish to examine this issue in relation to the development of the individual), and to psychologists (who are usually more concerned with populations or aggregate effects). The application of biometric genetic models might clarify this issue, and various suggestions are made regarding steps that need to be taken if such models are to be successfully applied.

Reproducibility of sonographic assessment of fetal liver length in diabetic pregnancies

OBJECTIVES

Assessing fetal liver size might be useful in monitoring the effectiveness of the treatment of diabetes in pregnancy. We aimed to assess the reproducibility of fetal liver-length measurement in pregnant women with diabetes.

METHODS

From 3 April 2006 to 5 December 2006, we assessed intraobserver and interobserver variation of fetal liver-length measurements on 55 sonograms in 44 pregnant women with diabetes, 34 of whom had gestational diabetes. The mean maternal age was 33 years, the mean maternal weight was 92 kg and the mean body mass index (BMI) was 33.7 kg/m(-2). The effect of covariates BMI, gestational age and maternal age on the reproducibility of fetal liver length was assessed by calculating intraobserver SD ratios. We compared liver length with abdominal circumference and gestational age. Nine of 12 sonographers scanned, on average, six women (range, 3-12) as the first sonographer, and all 12 sonographers scanned, on average, four women (range, 1-10) as the second sonographer. The data were analyzed using a hierarchical linear model.

RESULTS

Measurement of fetal liver length was reproducible. The intraobserver SD was 3.06 (95% CI, 2.68-3.59) mm; the interobserver SD was 2.17 (95% CI, 0.59-4.83) mm; the intraobserver correlation was 0.77 (95% CI, 0.63-0.87), and the interobserver correlation was 0.84 (95% CI, 0.51-0.99). The covariate effects were minimal, the SD for a 1-unit increase in the covariate was 1.06 for gestational age, 0.98 for BMI, and 0.97 for maternal age.

CONCLUSIONS

Measurement of fetal liver length in the diabetic pregnancy is reproducible. It is worthy of further investigation as a parameter for monitoring the effectiveness of treatment of the diabetic pregnancy.

Visual cues for the retrieval of landmark memories by navigating wood ants

Background

Even on short routes, ants can be guided by multiple visual memories. We investigate here the cues controlling memory retrieval as wood ants approach a one- or two-edged landmark to collect sucrose at a point along its base. In such tasks, ants store the desired retinal position of landmark edges at several points along their route. They guide subsequent trips by retrieving the appropriate memory and moving to bring the edges in the scene toward the stored positions.

Results

The apparent width of the landmark turns out to be a powerful cue for retrieving the desired retinal position of a landmark edge. Two other potential cues, the landmark's apparent height and the distance that the ant walks, have little effect on memory retrieval. A simple model encapsulates these conclusions and reproduces the ants' routes in several conditions. According to this model, the ant stores a look-up table. Each entry contains the apparent width of the landmark and the desired retinal position of vertical edges. The currently perceived width provides an index for retrieving the associated stored edge positions. The model accounts for the population behavior of ants and the idiosyncratic training routes of individual ants.

Discussion

Our results imply binding between the edge of a shape and its width and, further, imply that assessing the width of a shape does not depend on the presence of any particular local feature, such as a landmark edge. This property makes the ant's retrieval and guidance system relatively robust to edge occlusions.

Novel landmark-guided routes in ants

We review studies in which ants familiar with fixed routes between their nest and a feeding site are displaced from one of these destinations to an unfamiliar site away from the route. Ants can reach their goal from such novel release sites guided by distant landmarks. We suggest that an ant's ability to take such novel landmark-guided routes after displacement is a by-product of the robustness of normal route-following and is unlikely to reflect the ant's use of a map-like knowledge of its surroundings.

The co-activation of snapshot memories in wood ants

Insects can guide themselves along a familiar route to a familiar place by retrieving and using visual snapshots that they have stored both along the route and at their destination and moving so that their current views match the target snapshots. To learn more about the matching process, we have investigated the interaction of snapshots by engineering a situation in which ants simultaneously retrieve two sets of memories.

Ants were trained from a fixed start position to feed in one site, after which the feeder was switched to a new one. It could take up to 30 trials after the switch before the ants headed directly to the new food site. We suppose that during this transition phase ants retrieve memories appropriate for both sites. We compared the ants' behaviour for two different sized separations between feeder sites. When the sites are relatively close together, the initial headings of the ants' paths rotated gradually from aiming directly at the first food site to aiming at the second food site,suggesting that ants' paths are controlled by the weighted average of two simultaneously activated snapshot attractors. By contrast, when the food sites were further apart, initial headings switched abruptly between the two sites– ants either headed for food site 1 or for food site 2. We show that these differences in transition behaviour can be simulated by the co-activation of snapshot attractors of restricted spatial extent, such that features encoded in a snapshot are only recognised if they occur within a limited retinal distance of the stored position of the feature.

Supraclavicular radiotherapy must be limited laterally by the coracoid to avoid significant adjuvant breast nodal radiotherapy lymphoedema risk

This cross-sectional study aimed to investigate the effect of supraclavicular fossa (SCF) radiotherapy volumes as well as patient characteristics and nodal pathology on the development of lymphoedema. Ninety-one women who had received SCF nodal radiotherapy after axillary dissection were evaluated. Lymphoedema was defined by two measurements: limb volume difference 200 mL, or circumference difference 10 cm proximal or distal to the olecranon>2 cm. On univariate analysis, the addition of axillary to SCF radiotherapy, increasing width of the SCF field, increasing age, presence of extracapsular extension of nodal involvement and use of hormone treatment was associated with lymphoedema by either one or both definitions. For both definitions of lymphoedema, on multivariate analysis, increasing nodal radiotherapy volume remained significant (P=0.02 to 0.007), as did increased age (P=0.05 to 0.001). We conclude that conventionally fractionated SCF radiotherapy limited laterally by the coracoid process has a lymphoedema risk similar to that expected from axillary dissection alone and a lower risk than wider SCF fields with or without an axillary boost.

Bi-directional route learning in wood ants

Some ants and bees readily learn visually guided routes between their nests and feeding sites. They can learn the appearance of visual landmarks for the food-bound or homeward segment of the route when these landmarks are only present during that particular segment of their round trip. We show here that wood ants can also acquire landmark information for guiding their homeward path while running their food-bound path, and that this information may be picked up, when ants briefly reverse direction and retrace their steps for a short distance. These short periods of looking back tend to occur early in route acquisition and are more frequent on homeward than on food-bound segments.

Re-treatment of chronic hepatitis C patients after relapse: efficacy of peginterferon-alpha-2a (40 kDa) and ribavirin

We conducted a randomized multinational study to determine whether 48 weeks of re-treatment with peginterferon-alpha-2a (40 kDa) plus ribavirin would induce a sustained virological response (SVR) in relapsed chronic hepatitis C patients. Patients who had previously relapsed during 24 weeks of untreated follow-up, after having achieved an end-of-treatment virological response with 24 weeks of peginterferon-alpha-2a (40 kDa)/ribavirin combination therapy, within a phase III trial, were studied. Although the recommended dosage was the same as that used at the end of the initial trial, adjustments were permitted. Data on serious adverse events, or adverse events that resulted in dose reductions or discontinuations, were collected. Following re-treatment, the overall SVR rate in the 64 patients was 55%. The SVR rates in patients infected with hepatitis C virus (HCV) genotype 1 and non-1 genotypes were 51% and 63%, respectively. Early (week 12) virological responses were seen in 39 patients (61%) and were predictive of an SVR. Re-treatment was well tolerated. The most frequent adverse events recorded were fatigue (5%) and abdominal pain (3%). Dosages of peginterferon-alpha-2a (40 kDa) and/or ribavirin were modified because of adverse events in 3% and 13% of patients, and because of laboratory abnormalities in 23% and 5% of patients, respectively. Thus, a 48-week course of peginterferon-alpha-2a (40 kDa) plus ribavirin induces an SVR in 55% of patients who relapsed during follow-up after 24 weeks of combination therapy. Physicians should not hesitate to offer re-treatment to patients who relapse after an initial, 24-week course of combination therapy, or who have prematurely stopped treatment because, for example, of laboratory abnormalities.