2,552 research outputs found

    PACRR: A Position-Aware Neural IR Model for Relevance Matching

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    In order to adopt deep learning for information retrieval, models are needed that can capture all relevant information required to assess the relevance of a document to a given user query. While previous works have successfully captured unigram term matches, how to fully employ position-dependent information such as proximity and term dependencies has been insufficiently explored. In this work, we propose a novel neural IR model named PACRR aiming at better modeling position-dependent interactions between a query and a document. Extensive experiments on six years' TREC Web Track data confirm that the proposed model yields better results under multiple benchmarks.Comment: To appear in EMNLP201

    A tool for implementing privacy in Nano

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    © 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.We present a work in progress strategy for implementing privacy in Nano at the consensus level, that can be of independent interest. Nano is a cryptocurrency that uses an Open Representative Voting (ORV) as a consensus mechanism, a variant of Delegated Proof of Stake. Each transaction on the network is voted on by representatives, and each vote has a weight equal to the percentage of their total delegated balance. Every account can delegate their stake to any other account (including itself) and change it anytime it wants. The goal of this paper is to achieve a way for the consensus algorithm to function without knowing the individual balances of each account. The tool is composed of three different schemes. The first is a weighted threshold secret sharing scheme based on the Chinese Remainder Theorem for polynomial rings [1] and it's used to generate, in a distributed way, a secret that will be a private key of an additive ElGamal cryptosystem over elliptic curves (EC-EG) [2], which is additive homomorphic. The second scheme is the polynomials commitment scheme presented in [3] and is used to make the previous scheme verifiable, i.e., without the need of a trusted dealer. Finally, the third scheme is used to decrypt a ciphertext of the EC-EG cryptosystem without reconstructing the private key and, because of that, can be used multiple times.IEEEinfo:eu-repo/semantics/submittedVersio

    Supercritical Water Gasification of Eucalyptus Wood Chips Using NiFe2O4 as a Catalyst

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    In this work, the supercritical water gasification of eucalyptus wood chips has been investigated in relation to reaction temperature and presence of catalyst. Experiments were performed in a batch reactor at 450 ºC and 500 ºC with two different feed concentrations. This work wanted to evaluate mainly the gases were formed during the reactions. The gas products were analysed by gas chromatography. According to the results, it was found that eucalyptus wood chips reacted to form mainly H2, CH4 gases with little yield of CO2. Increasing the reaction temperature beyond 500 ºC led to the increasing production of both CH4 (around 31.1 mol%) and H2 (up to 38 mol%) gases and the liquid sample and solid residue have decreased. Generally, this work suggests that the SCWG has improved significantly the production of H2 but more experiments still necessary to verify the effects of other experimental parameters and to characterise the liquid sample and solid residue

    Development of a phage cocktail to prevent Proteus mirabilis biofilm formation in urinary catheters

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    Proteus mirabilis is an enterobacterium that causes catheter-associated urinary tract infections (CAUTIs) due to its ability to form crystalline biofilms on the surfaces. These CAUTIs are very difficult to treat, since the biofilm structures are extremely tolerant to high concentrations of antibiotics. Bacteririophages (phages) have been used widely to control and prevent a diversity of bacterial species, however a limited number of phages for P. mirabilis have been isolated and studied. Here we report the isolation of two novel virulent phages, the myovirus vB_PmiM_5460 and the podovirus vB_PmiP_5461 able to target respectively 57% and 100% of all Proteus strains tested in this study. Both phages have been characterized thoroughly and sequencing data revealed no traces of genes associated with lysogeny. To further evaluate the phages ability to prevent catheter colonization by Proteus, phages adherence to silicon surfaces was assessed. Both phages were able to adhere, but the extent of adhesion was found to be phage dependent. Further tests in phagecoated catheters using a dynamic biofilm model simulating CAUTIs, have shown a 90% significant reduction of P. mirabilis biofilm formation up to 168 h of catheterization. These results highlight the potential usefulness of the two isolated phages for the prevention of surface colonization by this bacterium

    Catalytic Properties and Recycling of NiFe 2 O 4 Catalyst for Hydrogen Production by Supercritical Water Gasification of Eucalyptus Wood Chips

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    Nickel iron oxide (NiFe2O4) catalyst was prepared by the combustion reaction method and characterized by XRD, N2 adsorption/desorption, thermogravimetric analysis (TG), and temperature programmed reduction (TPR). The catalyst presented a mixture of oxides, including the NiFe2O4 spinel and specific surface area of 32.4 m2 g−1. The effect of NiFe2O4 catalyst on the supercritical water gasification (SCWG) of eucalyptus wood chips was studied in a batch reactor at 450 and 500 °C without catalyst and with 1.0 g and 2.0 g of catalyst and 2.0 g of biomass for 60 min. In addition, the recyclability of the catalyst under the operating conditions was also tested using recovered and recalcined catalysts over three reaction cycles. The highest amount of H2 was 25 mol% obtained at 450 °C, using 2 g of NiFe2O4 catalyst. The H2 mol% was enhanced by 45% when compared to the non-catalytic test, showing the catalytic activity of NiFe2O4 catalyst in the WGS and the steam reforming reactions. After the third reaction cycle, the results of XRD demonstrated formation of coke which caused the deactivation of the NiFe2O4 and consequently, a 13.6% reduction in H2 mol% and a 5.6% reduction in biomass conversion

    The rhizoferrin biosynthetic gene in the fungal pathogen Rhizopus delemar is a novel member of the NIS gene family

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    This work was supported by the Natural Sciences and Engineering Research Council of Canada award to MM (grant number 611181). C. Carroll thanks Simon Fraser University for a travel and research award.Iron is essential for growth and in low iron environments such as serum many bacteria and fungi secrete ferric iron-chelating molecules called siderophores. All fungi produce hydroxamate siderophores with the exception of Mucorales fungi, which secrete rhizoferrin, a polycarboxylate siderophore. Here we investigated the biosynthesis of rhizoferrin by the opportunistic human pathogen, Rhizopus delemar. We searched the genome of R. delemar 99–880 for a homologue of the bacterial NRPS-independent siderophore (NIS) protein, SfnaD that is involved in biosynthesis of staphyloferrin A in Staphylococcus aureus. A protein was identified in R. delemar with 22% identity and 37% similarity with SfnaD, containing an N-terminal IucA/IucC family domain, and a C-terminal conserved ferric iron reductase FhuF-like transporter domain. Expression of the putative fungal rhizoferrin synthetase (rfs) gene was repressed by iron. The rfs gene was cloned and expressed in E.coli and siderophore biosynthesis from citrate and diaminobutane was confirmed using high resolution LC–MS. Substrate specificity was investigated showing that Rfs produced AMP when oxaloacetic acid, tricarballylic acid, ornithine, hydroxylamine, diaminopentane and diaminopropane were employed as substrates. Based on the production of AMP and the presence of a mono-substituted rhizoferrin, we suggest that Rfs is a member of the superfamily of adenylating enzymes. We used site-directed mutagenesis to mutate selected conserved residues predicted to be in the Rfs active site. These studies revealed that H484 is essential for Rfs activity and L544 may play a role in amine recognition by the enzyme. This study on Rfs is the first characterization of a fungal NIS enzyme. Future work will determine if rhizoferrin biosynthesis is required for virulence in Mucorales fungi.PostprintPeer reviewe
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