The conjugacy problem and related problems in lattice-ordered groups

We study, from a constructive computational point of view, the techniques used to solve the conjugacy problem in the "generic" lattice-ordered group Aut(R) of order automorphisms of the real line. We use these techniques in order to show that for each choice of parameters f,g in Aut(R), the equation xfx=g is effectively solvable in Aut(R).Comment: Small update

Acoustic Scattering from Mud Volcanoes and Carbonate Mounts

Submarine mud volcanoes occur in many parts of the world’s oceans and form an aperture for gas and fluidized mud emission from within the earth’s crust. Their characteristics are of considerable interest to the geology, geophysics, geochemistry, and underwater acoustics communities. For the latter, mud volcanoes are of interest in part because they pose a potential source of clutter for active sonar. Close-range (single-interaction) scattering measurements from a mud volcano in the Straits of Sicily show scattering10–15dB above the background. Three hypotheses were examined concerning the scattering mechanism: (1) gas entrained in sediment at/near mud volcano, (2) gas bubbles and/or particulates (emitted) in the water column, (3) the carbonate bio-construction covering the mud volcano edifice. The experimental evidence, including visual, acoustic, and nonacoustic sensors, rules out the second hypothesis (at least during the observation time) and suggests that, for this particular mud volcano the dominant mechanism is associated with carbonate chimneys on the mud volcano. In terms of scattering levels, target strengths of 4–14dB were observed from 800to3600Hz for a monostatic geometry with grazing angles of 3–5°. Similar target strengths were measured for vertically bistatic paths with incident and scattered grazing angles of 3–5° and 33–50°, respectively

Electrochemical Removal of Carbon Monoxide in Reformate Hydrogen for Fueling Proton Exchange Membrane Fuel Cells

A twin-cell electrochemical filter is demonstrated to reduce the CO concentration in reformate hydrogen. In this design, the potential and gas flow are switched between the two filter cells so that alternative CO adsorption and oxidation occur in each cell while providing a continuous flow of H2 to a fuel cell. The effects of filter switching time and applied potential on the CO concentration of gas exiting the filter are presented here for a CO concentration of 1000 ppm in nitrogen flowing at 100 cm3/min. The parasitic loss of hydrogen from a corresponding reformate stream was estimated to be 1.5%

Meso-Scale Seabed Quantification with Geoacoustic Inversion

Abstract Knowledge of sub-seabed geoacoustic properties, for example depth dependent sound speed and porosity, is of importance for a variety of applications. Here, we present a semi-automated geoacoustic inversion method for autonomous underwater vehicle data that objectively adapts model inference to seabed structure. Through parallelized trans-dimensional Bayesian inference, we infer seabed properties along a 12 km survey track on the scale of about 10 cm and 50 m in the vertical and horizontal, respectively. The inferred seabed properties include sound speed, attenuation, density, and porosity as a function of depth from acoustic reflection coefficient data. Parameter uncertainties are quantified, and the seabed properties agree closely with core samples at two control points and the layering structure with an independent sub-bottom seismic survey. Recovering high resolution seabed properties over large areas is shown to be feasible, which could become an important tool for marine industries, navies and oceanic research organizations

Coherence of signals reflected by the seafloor : numerical modeling vs experimental data

In this paper, we present the results of the analysis of the coherence (in the time domain) of an acoustic signal reflected by the seafloor. A spherical wave emitted by a broadband source is recorded on a vertical array after its reflection on the seafloor at two different shallow (between 100 m and 150 m) water sites. The temporal coherence is defined as the maximum of the correlation coefficient between two hydrophones. A numerical model was developed from the computation of the reflection coefficient of a spherical wave. The comparison between the experimental and the numerical results is very satisfactory and shows a significant dependence of the coherence on the geoacoustic structure of the seafloor. In a first analysis, this dependence is mainly due to the large scale structure of the seafloor and to the coherent part (i.e. reflection) of the acoustic field ; the differences between numerical and experimental results should be connected to the small-scale structure and to the incoherent part (i.e. scattering) of the field. These results give us some perspectives for the use of the temporal coherence in seafloor characterization applications.Dans cet article, nous présentons les premiers résultats de l’analyse de la fonction de cohérence (dans le domaine temporel) d’un signal acoustique réfléchi par le fond de la mer. Une onde sphérique émise par une source large bande est enregistrée sur une antenne verticale après réflexion sur le sol dans deux sites différents de faible profondeur d’eau (entre 100 et 150 mètres). La cohérence temporelle est définie comme étant le maximum du coefficient de corrélation entre les différents hydrophones. Un modèle numérique a été développé à partir du calcul du coefficient de réflexion d’une onde sphérique. La comparaison entre les résultats expérimentaux et les résultats numériques est très satisfaisante et montre une grande dépendance de la cohérence à la structure géoacoustique du sol marin. En première analyse, cette dépendance est principalement liée à la structure macro-échelle du sol ainsi qu’à la partie cohérente du champ acoustique ; les écarts entre les prédictions théoriques et les résultats expérimentaux seraient liés à la structure micro-échelle et à la partie incohérente du champ. Ces résultats ouvrent des perspectives quant à l’utilisation de la cohérence pour la caractérisation des fonds marins

Perivascular Nitric Oxide Activates Notch Signaling and Promotes Stem-like Character in PDGF-Induced Glioma Cells

SummaryeNOS expression is elevated in human glioblastomas and correlated with increased tumor growth and aggressive character. We investigated the potential role of nitric oxide (NO) activity in the perivascular niche (PVN) using a genetic engineered mouse model of PDGF-induced gliomas. eNOS expression is highly elevated in tumor vascular endothelium adjacent to perivascular glioma cells expressing Nestin, Notch, and the NO receptor, sGC. In addition, the NO/cGMP/PKG pathway drives Notch signaling in PDGF-induced gliomas in vitro, and induces the side population phenotype in primary glioma cell cultures. NO also increases neurosphere forming capacity of PDGF-driven glioma primary cultures, and enhances their tumorigenic capacity in vivo. Loss of NO activity in these tumors suppresses Notch signaling in vivo and prolongs survival of mice. This mechanism is conserved in human PDGFR amplified gliomas. The NO/cGMP/PKG pathway's promotion of stem cell-like character in the tumor PVN may identify therapeutic targets for this subset of gliomas

Ideal Gases in Time-Dependent Traps

We investigate theoretically the properties of an ideal trapped gas in a time-dependent harmonic potential. Using a scaling formalism, we are able to present simple analytical results for two important classes of experiments: free expansion of the gas upon release of the trap; and the response of the gas to a harmonic modulation of the trapping potential is investigated. We present specific results relevant to current experiments on trapped Fermions.Comment: 5 pages, 3 eps figure

Natural immunity to Ascaris lumbricoides associated with immunoglobulin E antibody to ABA-1 allergen and inflammation indicators in children, Infect. Immun. 67

Children putatively immune to the large roundworm Ascaris lumbricoides were identified in an area of Nigeria where infection is hyperendemic. Immunity was associated with higher levels of serum ferritin, C-reactive protein, and eosinophil cationic protein, indicating ongoing acute phase or inflammatory processes. In contrast, children who were susceptible to the infection had little serological evidence of inflammation despite their high parasite burdens. Immunoglobulin G (IgG) antibody activity in all subclasses was present in high titer in most children but appeared to have no protective function. Despite exceptionally high total IgE levels, there was no evidence that atopic responses to local common allergens was associated with natural immunity to Ascaris. Among those individuals who produced IgG antibody to recombinant ABA-1 allergen of Ascaris, the naturally immune group had significantly more IgE antibody to the allergen than did those susceptible to the infection. IgE antibody responses in conjunction with innate inflammatory processes therefore appear to associate with natural immunity to ascariasis. Helminth parasites are renowned for inducing elevated levels of serum immunoglobulin E (IgE) (20, 33), but the protective role of the antibody component of this response remains debatable The large roundworm of humans, Ascaris lumbricoides, inhabits the intestine, but juvenile-stage worms undergo a tissuemigratory phase involving the liver and lungs before returning to the intestine, where they mature to large adult worms. The pulmonary phase can cause potentially lethal hypersensitivity responses in infected individuals, particularly children, and worm material is notorious for the allergic reactions that it provokes in laboratory workers (33). A. lumbricoides infects a quarter of humanity and people can remain infected for much of their lives, although at the population level, intensity of infection decreases with age after a peak within the first decade of life in high-intensity areas We have examined a range of serum factors in African children living in an area highly endemic for A. lumbricoides, using the number of worms developing to maturity as a measure of immunity status. Quantifying worm burden is superior to using the number of eggs released, because egg production is a poor indicator of the number of adult worms present (15, 18) and may miss low-level infections. The children were examined for infection on two separate occasions, and those either consistently infected or putatively immune were identified. Neither the mechanisms by which immunity to A. lumbricoides operates nor the site within the body at which it is manifest is known. Therefore, in addition to measuring of antibody in the different isotypes, we examined a range of serological markers for inflammatory responses to provide an indication of the pathological processes which might accompany immune killing of the parasites. We find that natural immunity to Ascaris is associated with IgE antibody to a major allergen of the parasite and a serum protein profile consistent with ongoing inflammatory processes. MATERIALS AND METHODS Study population. The study site was in an area of Nigeria (Ile-Ife) in which more than 80% of the school children (5 to 15 years old) were infected with intestinal nematodes, particularly A. lumbricoides (for full details, see reference 18). A group of children were treated for their intestinal nematode infections, and their worm burdens were collected and counted over a 48-h period after anthelminthic treatment (phase 1). The anthelminthic used was Ketrax (levamisole; ICI Pharmaceuticals, Macclesfield, United Kingdom), and children were given the appropriate dosage according to the manufacturer's instructions. The exercise was repeated 6 months later (phase 2), at which time blood samples were collected from 92 of the children. The children were classified as follows: category 1, those with no worms on either of the two occasions (putatively immune); category 2, those with consistently light infections (1 to 24 worms in phase 1 and 1 to 8 worms in phase 2); or category 3, those who were consistently heavily infected or susceptible, i.e., had more than the population mean plus 1 standard deviation worm burden on both occasions. The means Ϯ standard deviations of the worm burdens in phases 1 and 2 were 11.02 Ϯ 13.7 and 3.5 Ϯ 5.6, respectively. Category 3 comprised children with worm counts of Ն25 after the first treatment and Ն9 after the second treatment. There were 22, 47, and 23 children in categories 1, 2, and 3, respectively. None of the children showed overt signs o

Teleology and logical mechanism

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43835/1/11229_2004_Article_BF00869605.pd