Reaction-diffusion navigation robot control: from chemical to VLSI analogic processors

We introduce a new methodology and experimental implementations for real-time wave-based robot navigation in a complex, dynamically changing environment. The main idea behind the approach is to consider the robot arena as an excitable medium, in which moving objects-obstacles and the target-are represented by sites of autowave generation: the target generates attractive waves, while the obstacles repulsive ones. The moving robot detects traveling and colliding wave fronts and uses the information about dynamics of the autowaves to adapt its direction of collision-free motion toward the target. This approach allows us to achieve a highly adaptive robot behavior and thus an optimal path along which the robot reaches the target while avoiding obstacles. At the computational and experimental levels, we adopt principles of computation in reaction-diffusion (RD) nonlinear active media. Nonlinear media where autowaves are used for information processing purposes can therefore be considered as RD computing devices. In this paper, we design and experiment with three types of RD processors: experimental and computational Belousov-Zhabotinsky chemical processor, computational CNN processor, and experimental RD-CNN very large-scale integration chip-the complex analog and logic computing engine (CACE1k). We demonstrate how to experimentally implement robot navigation using space-time snapshots of active chemical medium and how to overcome low-speed limitation of this "wetware" implementation in CNN-based silicon processors.     

Using alternative comparison populations to assess occupation-related mortality risk. Results for the high nickel alloys workers cohort

The focus of this article is to examine how the choice of comparison group affects the identification and interpretation of cause-specific health risks in occupational cohorts when different external control populations are used. The mortality experience of approximately 31,000 high nickel alloys workers is compared with the total US population and to local populations in geographic proximity to the plants. Generally, the patterns of relative risks derived for the total cohort and various subgroups are similar across the different comparison populations. Estimated elevated risks are usually lower when cohort mortality is compared with that of local populations. An overall significant 13% risk for lung cancer is noted when compared with that of the total US population. However, no significant excess is identified when local populations are used. Subset analysis identified significant excesses of colon cancer among nonwhite males (50%-150%) and kidney cancer among white male workers employed in melting (approximately 100%), irrespective of the comparison population.     

Mechanistic evidence of the partial oxidation of methane to formaldehdye over silica based oxide catalysts by temperature programmed reaction studies

The catalytic behaviour of SiO₂ supported MoO₂ and V₂O₅ catalysts in the partial oxidation of methane to formaldehyde with O₂ (MPO) in the range 400–800°C has been investigated by temperature programmed reaction (TPR) tests. Both the sequence of the onset temperature of product formation and the product distribution patterns signal that MPO on silica based oxide catalysts occurs mainly via a consecutive reaction path: CH₄ → HCHO → CO → CO₂. At T >/ 700°C a parallel surface assisted gas-phase reaction pathway leads to the formation of minor amounts of C₂ products both on SiO₂ and MoO₃/SiO₂ catalysts. The redox properties of MoO₃/SiO₂ and V₂O₅SiO₂ catalysts have been systematically evaluated by H₂ and CH₄ temperature programmed reduction (H₂-TPR, CH₄-TPR) measurements. H₂-TPR results do not account for the reactivity scale of oxide catalysts in the MPO. CH₄-TPR measurements indicate that the enhancement in the specific activity of the silica is controlled by the capability of MoO₃ and V₂O₅ promoters in providing ‘active’ lattice oxygen species.     

Barley β-Glucans-Containing Food Enhances Probiotic Performances of Beneficial Bacteria

Currently, the majority of prebiotics in the market are derived from non-digestible oligosaccharides. Very few studies have focused on non-digestible long chain complex polysaccharides in relation to their potential as novel prebiotics. Cereals β-glucans have been investigated for immune-modulating properties and beneficial effects on obesity, cardiovascular diseases, diabetes, and cholesterol levels. Moreover, β-glucans have been reported to be highly fermentable by the intestinal microbiota in the caecum and colon, and can enhance both growth rate and lactic acid production of microbes isolated from the human intestine. In this work, we report the effects of food matrices containing barley β-glucans on growth and probiotic features of four Lactobacillus strains. Such matrices were able to improve the growth rate of the tested bacteria both in unstressed conditions and, importantly, after exposure to in vitro simulation of the digestive tract. Moreover, the effect of β-glucans-containing food on bacterial adhesion to enterocyte-like cells was analyzed and a positive influence on probiotic-enterocyte interaction was observed.     

Room Temperature Ferrimagnetism and Ferroelectricity in Strained,Thin Films of BiFe0.5Mn0.5O3

Highly strained films of BiFe_0.5Mn_0.5O₃ (BFMO) grown at very low rates by pulsed laser deposition were demonstrated to exhibit both ferrimagnetism and ferroelectricity at room temperature and above. Magnetisation measurements demonstrated ferrimagnetism (T_C ～ 600K), with a room temperature saturation moment (M_S) of up to 90 emu/cc (～ 0.58 μ_B/f.u) on high quality (001) SrTiO₃. X‐ray magnetic circular dichroism showed that the ferrimagnetism arose from antiferromagnetically coupled Fe³⁺ and Mn³⁺. While scanning transmission electron microscope studies showed there was no long range ordering of Fe and Mn, the magnetic properties were found to be strongly dependent on the strain state in the films. The magnetism is explained to arise from one of three possible mechanisms with Bi polarization playing a key role. A signature of room temperature ferroelectricity in the films was measured by piezoresponse force microscopy and was confirmed using angular dark field scanning transmission electron microscopy. The demonstration of strain induced, high temperature multiferroism is a promising development for future spintronic and memory applications at room temperature and above.     

Picrotoxin blockade of invertebrate glutamate-gated chloride channels: subunit dependence and evidence for binding within the pore

Glutamate-gated chloride channels have been described in nematodes, insects, crustaceans, and mollusks. Subunits from the nematode and insect channels have been cloned and are phylogenetically related to the GABA and glycine ligand-gated chloride channels. Ligand-gated chloride channels are blocked with variable potency by the nonselective blocker picrotoxin. The first two subunits of the glutamate-gated chloride channel family, GluClalpha and GluClbeta, were cloned from the free living nematode Caenorhabditis elegans. In this study, we analyze the blockade of these novel channels by picrotoxin. In vitro synthesized GluClalpha and GluClbeta RNAs were injected individually or coinjected into Xenopus oocytes. The EC50 values for picrotoxin block of homomeric GluClalpha and GluClbeta were 59 microM and 77 nM, respectively. Picrotoxin block of homomeric GluClbeta channels was promoted during activation of membrane current with glutamate. In addition, recovery from picrotoxin block was faster during current activation by glutamate. A chimeric channel between the N-terminal extracellular domain of GluClalpha and the C-terminal membrane-spanning domain of GluClbeta localized the higher affinity picrotoxin binding site to the membrane-spanning domains of GluClbeta. A point mutation within the M2 membrane-spanning domain of GluClbeta reduced picrotoxin sensitivity >10,000-fold. We conclude that picrotoxin blocks GluCl channels by binding to a site accessible when the channel is open.     

"High risk" anterior basal skull fractures. Surgical treatment of 64 consecutive cases

Information on the number and causes of death is one of the basic components of a country's health information system. Data are usually derived from death certificates and health facility discharge summaries. There are usually several causes of error in the routine collection of this information. A criteria audit of death certificates is presented to assess these sources of error in Papua New Guinea. This procedure involved the systematic and critical analysis of hospital mortality as reported in death certificates. The audit is simple, cheap and useful for monitoring the quality of the mortality information which will be used in health planning and management. Quality criteria are defined and the completeness and relevance of the data audited are discussed. Recommendations for the improvement of the health information system are made.     

Aprotinin and deep hypothermic circulatory arrest: there are no benefits even when appropriate amounts of heparin are given

OBJECTIVE: To evaluate retrospectively the effect of 'high-dose' aprotinin on blood losses, donor blood requirements and morbid events on patients undergoing ascending aorta and/or aortic arch procedures with the employ of deep hypothermic circulatory arrest (HCA). METHODS: During the period 1987-1994, 39 patients underwent a thoracic aorta procedure with the employ of circulatory arrest; of these 18 (46.2%) were operated on during the period 1990-1994 and were given aprotinin intraoperatively following the 'high-dose' protocol (group I), while 21 (53.8%) who underwent surgery during the years 1987-1989, did not receive intraoperative aprotinin and served as historical controls (group II). Twenty-seven (69.2%) patients were male, 18 (46.2%) were operated on on an emergency basis, 15 (38.5%) were acute type A dissections, and two (5.1%) were redo-operations. Circulatory arrest times were not significantly different between the two groups (40 +/- 4 (S.E.) group I vs. 43 +/- 4 min group II, P = 0.62) likewise cardiopulmonary bypass (CPB) times (181 +/- 9 vs. 201 +/- 20 mm, P = 0.74) and the amount of heparin administered (32056 +/- 1435 vs. 31 691 +/- 1935 IU, P = 0.56). RESULTS: Postoperative blood loss was comparable between the two groups (1213 +/- 243 (median 850) group I vs. 1528 +/- 377 (median 880) ml group II, P = 0.87), as well as the number of units of donor blood transfused (9.4 +/- 3.0 (median 6) vs. 9.9 +/- 3.6, (median 5) P = 0.87), and revisions for bleeding (2/18, 11.1% vs. 3/21, 14.3%, P = 0.77). In-hospital mortality rate was not statistically different (5/18, 27.7% group I vs. 6/21, 28.6% group II, P = 0.92). There were no significant differences between the two groups in myocardial infarction (2/18, 11.1% vs. 0/21, 0%, P = 0.21), and postoperative renal failure rates (3/18, 16.7% vs. 2/21, 9.5%, P = 0.65). On the other hand, there was a trend towards an increased incidence of permanent neurological deficit (5/18, 27.7% group I vs. 1/21, 4.8% group II, P = 0.07) and towards a more complicated postoperative course (perioperative renal failure and/or myocardial infarction and/or neurological deficit either transient or permanent) (8/18, 44.4% group I vs. 4/21, 19% group II, P = 0.09) in group I patients. Forward stepwise logistic regression analysis, performed on the whole group of patients, identified chronic obstructive pulmonary disease (P = 0.010, Odds ratio (OR) = 5.7), aprotinin use (P = 0.017, OR = 5.1), and the number of units of blood collected intraoperatively by the cellsaver (P = 0.045, OR = 1.3/unit) as independent predictors of complicated postoperative course in the whole group of patients. CPB time (P = 0.040, OR = 1.032/min), circulatory arrest time (P = 0.053, OR = 1.22/min), and overall donor blood units transfused (P = 0.067, OR = 1.37/unit) emerged as independent risk factors for in-hospital mortality at multivariate analysis. CONCLUSIONS: Even when appropriate amounts of heparin are administered, 'high-dose' aprotinin probably is not an effective blood-sparing drug in deep HCA. Aprotinin should be employed cautiously in this clinical setting because of its possible correlation with an increased rate of postoperative morbid events.