2,253 research outputs found

    Co-firing of biomass with coals Part 1. Thermogravimetric kinetic analysis of combustion of fir (abies bornmulleriana) wood

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    The chemical composition and reactivity of fir (Abies bornmulleriana) wood under non-isothermal thermogravimetric (TG) conditions were studied. Oxidation of the wood sample at temperatures near 600 A degrees C caused the loss of aliphatics from the structure of the wood and created a char heavily containing C-O functionalities and of highly aromatic character. On-line FTIR recordings of the combustion of wood indicated the oxidation of carbonaceous and hydrogen content of the wood and release of some hydrocarbons due to pyrolysis reactions that occurred during combustion of the wood. TG analysis was used to study combustion of fir wood. Non-isothermal TG data were used to evaluate the kinetics of the combustion of this carbonaceous material. The article reports application of Ozawa-Flynn-Wall model to deal with non-isothermal TG data for the evaluation of the activation energy corresponding to the combustion of the fir wood. The average activation energy related to fir wood combustion was 128.9 kJ/mol, and the average reaction order for the combustion of wood was calculated as 0.30

    Order of Magnitude Smaller Limit on the Electric Dipole Moment of the Electron

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    The Standard Model of particle physics is known to be incomplete. Extensions to the Standard Model, such as weak-scale supersymmetry, posit the existence of new particles and interactions that are asymmetric under time reversal (T) and nearly always predict a small yet potentially measurable electron electric dipole moment (EDM), d_e, in the range of 10^(−27) to 10^(−30) e·cm. The EDM is an asymmetric charge distribution along the electron spin (S) that is also asymmetric under T. Using the polar molecule thorium monoxide, we measured d_e = (–2.1±3.7_(stat)±2.5_(syst)) × 10−29 e·cm. This corresponds to an upper limit of ❘d_e❘ < 8.7 × 10^(−29) e·cm with 90% confidence, an order of magnitude improvement in sensitivity relative to the previous best limit. Our result constrains T-violating physics at the TeV energy scale

    Effects of antenatal betamethasone on preterm human and mouse ductus arteriosus: comparison with baboon data.

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    BackgroundAlthough studies involving preterm infants ≤34 weeks gestation report a decreased incidence of patent ductus arteriosus after antenatal betamethasone, studies involving younger gestation infants report conflicting results.MethodsWe used preterm baboons, mice, and humans (≤276/7 weeks gestation) to examine betamethasone's effects on ductus gene expression and constriction both in vitro and in vivo.ResultsIn mice, betamethasone increased the sensitivity of the premature ductus to the contractile effects of oxygen without altering the effects of other contractile or vasodilatory stimuli. Betamethasone's effects on oxygen sensitivity could be eliminated by inhibiting endogenous prostaglandin/nitric oxide signaling. In mice and baboons, betamethasone increased the expression of several developmentally regulated genes that mediate oxygen-induced constriction (K+ channels) and inhibit vasodilator signaling (phosphodiesterases). In human infants, betamethasone increased the rate of ductus constriction at all gestational ages. However, in infants born ≤256/7 weeks gestation, betamethasone's contractile effects were only apparent when prostaglandin signaling was inhibited, whereas at 26-27 weeks gestation, betamethasone's contractile effects were apparent even in the absence of prostaglandin inhibitors.ConclusionsWe speculate that betamethasone's contractile effects may be mediated through genes that are developmentally regulated. This could explain why betamethasone's effects vary according to the infant's developmental age at birth

    Co-evolution of density and topology in a simple model of city formation

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    We study the influence that population density and the road network have on each others' growth and evolution. We use a simple model of formation and evolution of city roads which reproduces the most important empirical features of street networks in cities. Within this framework, we explicitely introduce the topology of the road network and analyze how it evolves and interact with the evolution of population density. We show that accessibility issues -pushing individuals to get closer to high centrality nodes- lead to high density regions and the appearance of densely populated centers. In particular, this model reproduces the empirical fact that the density profile decreases exponentially from a core district. In this simplified model, the size of the core district depends on the relative importance of transportation and rent costs.Comment: 13 pages, 13 figure

    Genome-wide analysis of ivermectin response by Onchocerca volvulus reveals that genetic drift and soft selective sweeps contribute to loss of drug sensitivity

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    Treatment of onchocerciasis using mass ivermectin administration has reduced morbidity and transmission throughout Africa and Central/South America. Mass drug administration is likely to exert selection pressure on parasites, and phenotypic and genetic changes in several Onchocerca volvulus populations from Cameroon and Ghana-exposed to more than a decade of regular ivermectin treatment-have raised concern that sub-optimal responses to ivermectin's anti-fecundity effect are becoming more frequent and may spread.Pooled next generation sequencing (Pool-seq) was used to characterise genetic diversity within and between 108 adult female worms differing in ivermectin treatment history and response. Genome-wide analyses revealed genetic variation that significantly differentiated good responder (GR) and sub-optimal responder (SOR) parasites. These variants were not randomly distributed but clustered in ~31 quantitative trait loci (QTLs), with little overlap in putative QTL position and gene content between the two countries. Published candidate ivermectin SOR genes were largely absent in these regions; QTLs differentiating GR and SOR worms were enriched for genes in molecular pathways associated with neurotransmission, development, and stress responses. Finally, single worm genotyping demonstrated that geographic isolation and genetic change over time (in the presence of drug exposure) had a significantly greater role in shaping genetic diversity than the evolution of SOR.This study is one of the first genome-wide association analyses in a parasitic nematode, and provides insight into the genomics of ivermectin response and population structure of O. volvulus. We argue that ivermectin response is a polygenically-determined quantitative trait (QT) whereby identical or related molecular pathways but not necessarily individual genes are likely to determine the extent of ivermectin response in different parasite populations. Furthermore, we propose that genetic drift rather than genetic selection of SOR is the underlying driver of population differentiation, which has significant implications for the emergence and potential spread of SOR within and between these parasite populations

    Three newly discovered sub-Jupiter-mass planets: WASP-69b and WASP-84b transit active K dwarfs and WASP-70Ab transits the evolved primary of a G4+K3 binary

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    We report the discovery of the transiting exoplanets WASP-69b, WASP-70Ab and WASP-84b, each of which orbits a bright star (V ∼ 10). WASP-69b is a bloated Saturn-mass planet (0.26 MJup, 1.06 RJup) in a 3.868-d period around an active, ∼1-Gyr, mid-K dwarf. ROSAT detected X-rays 60±27 arcsec from WASP-69. If the star is the source then the planet could be undergoing mass-loss at a rate of ∼1012 g s−1. This is one to two orders of magnitude higher than the evaporation rate estimated for HD 209458b and HD 189733b, both of which have exhibited anomalously large Lyman α absorption during transit. WASP-70Ab is a sub-Jupiter-mass planet (0.59 MJup, 1.16 RJup) in a 3.713-d orbit around the primary of a spatially resolved, 9–10-Gyr, G4+K3 binary, with a separation of 3.3 arcsec (≥800 au). WASP-84b is a sub-Jupiter-mass planet (0.69 MJup, 0.94 RJup) in an 8.523-d orbit around an active, ∼1-Gyr, early-K dwarf. Of the transiting planets discovered from the ground to date, WASP-84b has the third-longest period. For the active stars WASP-69 and WASP-84, we pre-whitened the radial velocities using a low-order harmonic series. We found that this reduced the residual scatter more than did the oft-used method of pre-whitening with a fit between residual radial velocity and bisector span. The system parameters were essentially unaffected by pre-whitening

    From Stop to Start: Tandem Gene Arrangement, Copy Number and Trans-Splicing Sites in the Dinoflagellate Amphidinium carterae

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    Dinoflagellate genomes present unique challenges including large size, modified DNA bases, lack of nucleosomes, and condensed chromosomes. EST sequencing has shown that many genes are found as many slightly different variants implying that many copies are present in the genome. As a preliminary survey of the genome our goal was to obtain genomic sequences for 47 genes from the dinoflagellate Amphidinium carterae. A PCR approach was used to avoid problems with large insert libraries. One primer set was oriented inward to amplify the genomic complement of the cDNA and a second primer set would amplify outward between tandem repeats of the same gene. Each gene was also tested for a spliced leader using cDNA as template. Almost all (14/15) of the highly expressed genes (i.e. those with high representation in the cDNA pool) were shown to be in tandem arrays with short intergenic spacers, and most were trans-spliced. Only two moderately expressed genes were found in tandem arrays. A polyadenylation signal was found in genomic copies containing the sequence AAAAG/C at the exact polyadenylation site and was conserved between species. Four genes were found to have a high intron density (>5 introns) while most either lacked introns, or had only one to three. Actin was selected for deeper sequencing of both genomic and cDNA copies. Two clusters of actin copies were found, separated from each other by many non-coding features such as intron size and sequence. One intron-rich gene was selected for genomic walking using inverse PCR, and was not shown to be in a tandem repeat. The first glimpse of dinoflagellate genome indicates two general categories of genes in dinoflagellates, a highly expressed tandem repeat class and an intron rich less expressed class. This combination of features appears to be unique among eukaryotes
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