A memory-based approach to sensory-motor coordination

In this work a visual-based autonomous system capable of memorizing and recalling sensory-motor associations is presented. The robot's behaviors are based on learned associations between its sensory inputs and its motor actions. Perception is divided into two stages. The first one is functional: algorithmic procedures extract in real time visual features such as disparity and local orientation from the input images. The second stage is mnemonic: the features produced by the different functional areas are integrated with motor information and memorized or recalled. An efficient memory organization and fast information retrieval enables the robot to learn to navigate and to avoid obstacles without need of an internal metric reconstruction of the external environment. Received: 22 November 1996 / Accepted: 18 November 1997     

A tentative method for detecting resistance to gamma-HCH in three bruchid beetles

A discriminating dose test technique for the detection of gamma-HCH resistance employing exposure on impregnated filter papers and using knockdown at 24 hr as the criterion showed that out of 25 strains, mainly of field-collected Bruchidae, 16 could be considered fully susceptible. The test indicated that resistance occurs in Zabrotes subfasciatus (Boh.) from Colombia and Mexico, Callosobruchus chinensis (L.) from India and Callosobruchus maculatus (F.) from Malawi and Senegal. No evidence of resistance was found in 5 strains of Acanthoscelides obtectus (Say), in 2 strains of Callosobruchus rhodesianus (Pic) or one strain of Callosobruchus analis (F).     

Microscopic infrared mapping of chloromethylated polystyrene resin beads

In solid-phase combinatorial chemistry, analyses are performed using a wide range of analytical techniques ranging from gel-phase nuclear magnetic resonance (NMR) to colorimetric tests to elemental analysis. However, these techniques cannot be used to interrogate functional group distribution at the single-bead level. This paper explores the feasibility of using Fourier transform infrared (FT-IR) microscopy to examine site distribution on chloromethylated polystyrene resin beads and to quantify the loading after coupling with 4-cyanophenol, an IR tagging agent. FT-IR microscopy also provides a unique opportunity to better understand the reactivity of highly cross-linked polymer beads under a range of chemical conditions.     

Oxidation-responsive polymeric vesicles

Vesicles formed in water by synthetic macro-amphiphiles have attracted much attention as nanocontainers having properties that extend the physical and chemical limits of liposomes. We sought to develop ABA block copolymeric amphiphiles that self-assemble into unilamellar vesicles that can be further oxidatively destabilized. We selected poly(ethylene glycol) (PEG) as the hydrophilic A blocks, owing to its resistance to protein adsorption and low toxicity. As hydrophobic B blocks, we selected poly(propylene sulphide) (PPS), owing to its extreme hydrophobicity, its low glass-transition temperature, and most importantly its oxidative conversion from a hydrophobe to a hydrophile, poly(propylene sulphoxide) and ultimately poly(propylene sulphone). This is the first example of the use of oxidative conversions to destabilize such carriers. This new class of oxidation-responsive polymeric vesicles may find applications as nanocontainers in drug delivery, biosensing and biodetection.     

Deploying a metal adsorbent in situ: a technique for indicating bioavailable Cd(II) in marine waters

This paper reports a study into the deployment of a metal adsorbent in situ to estimate bioavailable Cd(II) in marine waters. Eight adsorbents were screened in the laboratory to test their ability to accumulate Cd(II) from deionised water and artificial seawater, and an oxidised activated carbon was selected for further investigation. The adsorption isotherm at Cd(II) concentrations 0.16-38 microgl(-1) and at salinity 15 followed the Freundlich equation. The adsorbent was contained in nylon bags (pore size 35 microm) and dialysis tubes (membrane pore size 2 nm) to produce deployable devices and to investigate the effect of housing material on Cd(II) accumulation. The devices were tested in the laboratory and deployed at four field sites for up to 3 weeks. The adsorbent in the nylon bags reached equilibrium towards the end of this period and the measured contents were in good agreement with expected contents predicted from known seawater Cd(II) concentrations and the adsorption isotherm. The dialysis tubes accumulated significantly lower amounts of Cd(II) than the nylon bags, probably due to an initial lag as Cd(II) diffused into the dialysis bag and due to biofouling which reduced diffusion. The relationship between concentrations of Cd(II) accumulated by the mussels (indicating the bioavailable Cd(II) fraction) and the devices at different field sites could be described by the Freundlich model. The goodness of fit of this relationship was better for the dialysis tubes than the nylon bags. The adsorbent in the nylon bags may have collected small particles from seawater which affected the Cd(II) analysis. Both devices demonstrate potential as indicators of the relative bioavailable fraction of Cd(II) to Mytilus edulis in marine waters.     

Alignment of three-dimensional molecules using an image recognition algorithm

This paper describes a novel approach, based on image recognition in two dimensions, for the atom-based alignment of two rigid molecules in three dimensions. The atoms are characterised by their partial charges and their positions relative to the remaining atoms in the molecule. Based on this information, a cost of matching a pair of atoms, one from each molecule, is assigned to all possible pairs. A preliminary set of intermolecular atom equivalences that minimises the total atom matching cost is then determined using an algorithm for solving the linear assignment problem. Several geometric heuristics are described that aim to reduce the number of atom equivalences that are inconsistent with the 3D structures. Those that remain are used to calculate an alignment transformation that achieves an optimal superposition of atoms that have a similar local geometry and partial charge. This alignment is then refined by calculating a new set of equivalences consisting of atom pairs that are approximately overlaid, irrespective of partial charge. A range of examples is provided to demonstrate the efficiency and effectiveness of the method.     

An evaluation of four types of railway pedestrian crossing safety intervention

This study evaluated a programme of interventions designed to reduce the incidence of illegal and unsafe crossing of a rail corridor at a city station by boys on their way to and from the adjacent high school in Auckland, New Zealand. The boys were observed crossing before, during, and after implementation of each intervention; in addition, surveys were carried out before and after the programme to discover the boys' attitudes. Rail safety education in school, punishment for every unsafe crossing (continuous punishment), and punishment occasionally for unsafe crossing (intermittent punishment) were associated with significant decreases in unsafe crossing compared with that observed prior to any intervention. General communications about rail safety were not associated with significant decreases in unsafe crossing. When interventions were examined consecutively, unsafe crossing was significantly reduced between the communications and education phases, and even more so between education and continuous punishment, but there was no statistically significant difference in frequency of unsafe crossing between continuous and intermittent punishment. It was concluded that punishment may be more effective in reducing unsafe behaviour in this type of situation than targeted education, and is much more effective than communications to heighten awareness.     

Simultaneous localization and odometry self calibration for mobile robot

This paper presents both the theory and the experimental results of a method allowing simultaneous robot localization and odometry error estimation (both systematic and non-systematic) during the navigation. The estimation of the systematic components is carried out through an augmented Kalman filter, which estimates a state containing the robot configuration and the parameters characterizing the systematic component of the odometry error. It uses encoder readings as inputs and the readings from a laser range finder as observations. In this first filter, the non-systematic error is defined as constant and it is overestimated. Then, the estimation of the real non-systematic component is carried out through another Kalman filter, where the observations are obtained by two subsequent robot configurations provided by the previous augmented Kalman filter. There, the systematic parameters in the model are regularly updated with the values estimated by the first filter. The approach is theoretically developed for both the synchronous and the differential drive. A first validation is performed through very accurate simulations where both the drive systems are considered. Then, a series of experiments are carried out in an indoor environment by using a mobile platform with a differential drive.     

Selection of artificial neural network models for survival analysis with Genetic Algorithms

In follow-up clinical studies, the main time end-point is the failure from a specific starting point (e.g. treatment, surgery). A deeper investigation concerns the causes of failure. Statistical analysis typically focuses on the study of the cause specific hazard functions of possibly censored survival data. In the framework of discrete time models and competing risks, a multilayer perceptron was already proposed as an extension of generalized linear models with multinomial errors using a non-linear predictor (PLANNCR). According to standard practice, weight-decay was adopted to modulate model complexity. A Genetic Algorithm is considered for the complexity control of PLANNCR allowing to regularize independently each parameter of the model. The ICOMP information criterion is used as fitness function. To demonstrate the criticality and the benefits of the technique an application to a case series of 1793 women with primary breast cancer without axillary lymph node involvement is presented.