Using Absolute Metric Maps to Close Cycles in a Topological Map

In simultaneous localisation and mapping (SLAM) the correspondence problem, specifically detecting cycles, is one of the most difficult challenges for an autonomous mobile robot. In this paper we show how significant cycles in a topological map can be identified with a companion absolute global metric map. A tight coupling of the basic unit of representation in the two maps is the key to the method. Each local space visited is represented, with its own frame of reference, as a node in the topological map. In the global absolute metric map these local space representations from the topological map are described within a single global frame of reference. The method exploits the overlap which occurs when duplicate representations are computed from different vantage points for the same local space. The representations need not be exactly aligned and can thus tolerate a limited amount of accumulated error. We show how false positive overlaps which are the result of a misaligned map, can be discounted.     

The determination of myo-inositol hexakisphosphate (phytate)

A method for the determination of myo-inositol hexakisphosphate (phytate; P₆-myo-inositol) in plant material has been devised which involves the extraction of the sample with 0.3m trichloroacetic acid (TCA), application of the diluted extract to an anion-exchange resin column in the TCA form, and elution of all phosphoric esters, other than P₆myo-inositol, with 0.1M TCA. P₆-myo-inositol is then eluted from the column with 1.0M HCl and a suitable aliquot of this solution is assayed for phosphorus.     

Hydrodynamic behavior of a liquid-solid fluidized-bed reactor for the bioconversion of coal particles to liquid products

A predictive mathematical model based on particle convection and dispersion is presented for a liquid fluidized bed of coal particles. The numerical representation can follow transient behavior of liquid fluidized beds that contain a defined particle-size distribution. The calculations exhibited excellent agreement when compared to experimental transient pressure-drop data from a column containing particles of Illinois No. 6 bituminous coal in the size range of 20–120 μm. In addition, the model was used to simulate the effect of periodic (hourly) liquid velocity step changes on elutriation of small particles from a given particle-size distribution of 34.5–75.5 μm. For the situation tested, the calculations indicate that (a) the column does not reach a steady state between velocity changes and (b) that higher initial particle elutriation rates decay to lower values until no more particles elutriate from the column.     

Self-diffusion in Solutions of Carboxylated Acrylic Polymers as Studied by Pulsed Field Gradient NMR. 1. Solvent Diffusion Studies

The diffusion constants of solvent in solutions of carboxylated acrylic random copolymers in isopropanol (IPA) have been investigated using the PFG NMR technique. The copolymers are composed of butyl methacrylate and methacrylic acid with a range of molar ratios (BMA/MAA 100/0 through to 60/40 in 10 mol% steps). It was found that the echo attenuation function depended on the diffusion time, and experiments with short and long diffusion times have been analysed separately. Two questions are addressed: the first concerns the influence of concentration on the polymer aggregation in solution, and the second concerns the influence of the BMA/MAA molar ratio on the diffusion constants of the solvent. The data obtained have been discussed using established physical models for diffusion. Using the model of Wang gave the relative mass of bound solvent per mass of polymer which increased with the mol% of MAA in the copolymer.     

Faecal chymotrypsin in small for gestational age infants: effects of nucleotides and breast feeding

The effect of diet on pancreatic exocrine function, measured by faecal chymotrypsin activity (FCA), was studied longitudinally in three groups of small for gestational age (SGA) infants in the first six months of life. The three groups comprised breastfed infants (group B), those randomly allocated to receive a standard infant formula (group S), or the same formula supplemented with nucleotides (group N). The three groups did not differ in their birthweight or gestational age. Nucleotide supplementation of infant formula improves catchup growth in SGA infants but whether this is due to effects on the gastrointestinal mucosa or the exocrine pancreas is not known. There were no differences in FCA at study entry but by one month group B had significantly lower values than the other groups, and this was maintained at 2, 4, and 6 months. Groups N and S did not differ significantly at any time point. Nucleotide supplementation of infant formula does not influence pancreatic exocrine function and its effect on growth is unlikely, therefore, to be mediated through the pancreas. This study shows that breast feeding is associated with lower FCA which may be related to the lower protein content of human milk. Reliable interpretation of FCA in young infants requires information about their diet.     

The importance of accurate lesion placement in posteroventral pallidotomy. Report of two cases

OBJECTIVES: The effects of anemia of prematurity during bronchopulmonary dysplasia (BPD) as well as on the metabolic and erythropoietic functions were determined before and after a transfusion. Fourteen anemic (Hb range: 65-88 gm/L), oxygen dependent (fraction of inspired oxygen < or = 35%), nonventilated, preterm infants with BPD were studied at a postnatal age of 6 +/- 2 weeks. STUDY DESIGN: Cardiac output, heart rate, mean velocity of circumferential fiber shortening, shortening fraction (SF), and stroke volume were assessed by pulsed and continuous wave Doppler echocardiography. Values for resting oxygen consumption, carbon dioxide production, and energy expenditure were obtained by indirect calorimetry. The affinity of oxygenated hemoglobin was determined by a blood oxygen dissociation analyzer. RESULTS: An increased hemoglobin level resulted in a suppression of erythropoietin secretion (p < 0.001), whereas heart rate, cardiac output, stroke volume, and SF decreased (p < 0.05). Weight gain before and after transfusion were similar. Plasma lactate levels decreased from 1.6 +/- 0.3 to 1.2 +/- 0.3. Oxygen consumption, carbon dioxide production, and energy expenditure were not affected. CONCLUSIONS: Anemia of prematurity and BPD increase heart rate, cardiac output, stroke volume, and SF. These hemodynamic compensatory responses are normalized by transfusion.     

Three-dimensional gait analysis in spina bifida

This study was designed to determine gait patterns in children with lumbar and sacral neurologic level spina bifida. We studied a group of 28 children: 10 had L4-level lesions and a mean age of 11 years; eight had L5-level lesions and a mean age of 8 years; and 10 had S1-level lesions with a mean age of 12 years. A group of 15 normal children, mean age 10 years, was used for comparison. Each child underwent three-dimensional gait analysis using the Vicon system. We found that there were recognisable gait patterns for each level of spina bifida and that the abnormalities accurately reflected the muscle deficiencies present. The gait patterns approximated more closely to those of the normal group as the neurological level descended. The most important findings were of increased pelvic obliquity and rotation with hip abduction in stance (reflecting the gross Trendelenburg-type gait seen in these children) and persistent knee flexion throughout stance as a result of the absence of the plantar flexion-knee extension couple. We found that gait was not improved by tendon transfers performed either at the hip (posterolateral psoas transfer) or at the ankle (tibialis anterior transfer).     

Antitumor activity of the novel human breast cancer growth inhibitor, mammary-derived growth inhibitor-related gene, MRG

A novel human tumor growth inhibitor was identified by differential cDNA sequencing. The predicted amino acid sequence of this tumor-suppressing factor has a significant sequence homology to mouse mammary-derived growth inhibitor and thus was named mammary-derived growth inhibitor-related gene (MRG). MRG was found to be expressed in normal and benign human breast tissues but not in breast carcinomas. In situ hybridization analysis demonstrated a stage-specific MRG expression as follows. MRG was barely detectable in breast carcinomas, showed partial and weak expression in benign hyperplasia, but was expressed at a high level in normal breast epithelial cells. To determine if MRG can modulate in vivo growth of human breast cancers, we transfected a full-length MRG cDNA into MDA-MB-231 human breast cancer cells and studied the orthotopic growth of MRG transfectants versus control transfectants in the mammary fat pad of athymic nude mice. Overexpression of MRG in human breast cancer cells significantly suppressed cell proliferation in vitro and tumor growth in an orthotopic nude mouse model. These results suggest that MRG has tumor-suppressing activity, and the loss of MRG expression may be involved in the development and progression of breast cancer.