3,128 research outputs found

    Lunar impact flashes from Geminids, analysis of luminous efficiencies and the flux of large meteoroids on Earth

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    We analyze lunar impact flashes recorded by our team during runs in December 2007, 2011, 2013 and 2014. In total, 12 impact flashes with magnitudes ranging between 7.1 and 9.3 in V band were identified. From these, 9 events could be linked to the Geminid stream. Using these observations the ratio of luminous energy emitted in the flashes with respect to the kinetic energy of the impactors for meteoroids of the Geminid stream is estimated. By making use of the known Geminids meteoroid flux on Earth we found this ratio to be 2.1x10−3^{-3} on average. We compare this luminous efficiency with other estimations derived in the past for other meteoroid streams and also compare it with other estimations that we present here for the first time by making use of crater diameter measurements. We think that the luminous efficiency has to be revised downward, not upward, at least for sporadic impacts. This implies an increase in the influx of kilogram-sized and larger bodies on Earth that has been derived thus far through the lunar impact flash monitoring technique

    The role of ERP in business model innovation: Impetus or impediment

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    Purpose This research explores the moderating role of Enterprise Resource Planning (ERP) in (Business Model (BM) innovation by comparing two groups of Small and Medium-sized Enterprises (SMEs) that are still in the process of considering adoption of ERP or already have implemented ERP. In particular, the aim is to see whether ERP enables or hampers the relationship between BM experimentation, i.e. the process of BM innovation, and BM performance. An important mediator, with a focus on downstream value delivery and creation, is the novelty of the BM in question. Design/methodology/approach This research is based on a large quantitative study among Spanish firms that are engaged in BM innovation activities and in different phases of implementing ERP. A representative sample of 208 Spanish firms engaged in Business Model Innovation from different sectors was used to collect data, which was analysed using heterotrait-monotrait (HTMT) for scaling and Structural Equation Modelling (SEM) for model testing. Findings Quantitative findings show that there is a direct positive impact of BM experimentation on BM performance for firms that did not implement an ERP, while downstream novelty leads to improved value capture due to increased efficiency and the associated cost reduction. By contrast, firms with ERP show a better performance, depending on the degree of the downstream novelty of the BM. Originality/value There is no previous research exploring the moderating role of ERP in BM Innovation for SMEs. This is the first study to examine whether BM experimentation affects BM performance and value capturing, as mediated by BM novelty and moderated by implementation by ERP.publishedVersio

    Drive a Website Performance Using Web Analytics: A Case Study.

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    With the introduction of Web Analytics into Web Marketing, organizations now have the opportunity to measure, track, and analyze the behavior of their website users. The REAN model, standing for Reach, Engage, Activate and Nurture, appeared to be the most relevant model to plan and measure activities. This model is used to set goals, objectives and define metrics in order to improve Website performances using Web Analytics. The main research objective is to establish a list of optimization actions (based on academic papers, official sources, white papers and best practices) to be implemented, and to test if those actions had a positive impact on the website performance. Preliminary findings from this research-in-progress paper may assist managers on: 1) how to attract new visitors in order to expand traffic, 2) how to transform visitors into users, and increase registrations, and 3) how to build a loyal audience and make visitors come back

    A Hybrid Piece-Wise Slowdown Model for Concurrent Kernel Execution on GPU

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    Current execution of kernels on GPUs allows improving the use of hardware resources and reducing the execution time of co-executed kernels. In addition, efficient kernel-oriented scheduling policies pursuing criteria based on fairness or Quality of Service can be implemented. However, achieved co-executing performance strongly depends on how GPU resources are partitioned between kernels. Thus, precise slowdown models that predict accurate co-execution performance must be used to fulfill scheduling policy requirements. Most recent slowdown models work with Spatial Multitask (SMT) partitioning, where Stream Multiprocessors (SMs) are distributed among tasks. In this work, we show that Simultaneous Multikernel (SMK) partitioning, where kernels share the SMs, obtains better performance. However, kernel interference in SMK occurs not only in global memory, as in the SMT case, but also within the SM, leading to high prediction errors. Here, we propose a modification of a previous state-of-the-art slowdown model to reduce median prediction error from 27.92% to 9.50%. Moreover, this new slowdown model is used to implement a scheduling policy that improves fairness by 1.41x on average compared to even partitioning, whereas previous models reach only 1.21x on average.Universidad de MĂĄlaga. Campus de Excelencia Internacional AndalucĂ­a Tech P18-FR-3130 UMA20-FEDERJA-059 PID2019-105396RB-I0

    Robust and Cooperative Image-Based Visual Servoing System Using a Redundant Architecture

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    The reliability and robustness of image-based visual servoing systems is still unsolved by the moment. In order to address this issue, a redundant and cooperative 2D visual servoing system based on the information provided by two cameras in eye-in-hand/eye-to-hand configurations is proposed. Its control law has been defined to assure that the whole system is stable if each subsystem is stable and to allow avoiding typical problems of image-based visual servoing systems like task singularities, features extraction errors, disappearance of image features, local minima, etc. Experimental results with an industrial robot manipulator based on Schunk modular motors to demonstrate the stability, performance and robustness of the proposed system are presented

    Tumor Escape Phenotype in Bladder Cancer Is Associated with Loss of HLA Class I Expression, T-Cell Exclusion and Stromal Changes

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    Cancer eradication and clinical outcome of immunotherapy depend on tumor cell immunogenicity, including HLA class I (HLA-I) and PD-L1 expression on malignant cells, and on the characteristics of the tumor microenvironment, such as tumor immune infiltration and stromal reaction. Loss of tumor HLA-I is a common mechanism of immune escape from cytotoxic T lymphocytes and is linked to cancer progression and resistance to immunotherapy with the inhibitors of PD-L1/PD-1 signaling. Here we observed that HLA-I loss in bladder tumors is associated with T cell exclusion and tumor encapsulation with stromal elements rich in FAP-positive cells. In addition, PD-L1 upregulation in HLA-I negative tumors demonstrated a correlation with high tumor grade and worse overall- and cancer-specific survival of the patients. These changes define common immuno-morphological signatures compatible with cancer immune escape and acquired resistance to therapeutic interventions across different types of malignancy. They also may contribute to the search of new targets for cancer treatment, such as FAP-expressing cancer-associated fibroblasts, in refractory bladder tumors.ISCIII Research Institute co-financed by the European Union (FED-ER-Fondo Europeo de Desarrollo Regional) (RETIC RD 06/020, RD09/0076/00165PI14/01978, PI16/00752, Q2827015E, PI17/00197, PT17/0015/0041) and by the Junta de AndalucĂ­a in Spain (Groups CTS-143, CTS-695, CTS3952, CVI-4740).AbbottSpanish Research Institute IDI-URO, Madri

    Enzymatic oxidation of oleuropein and 3-hydroxytyrosol by laccase, peroxidase and tyrosinase.

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    The oxidation of oleuropein and 3‐hydroxytyrosol by oxidases laccase, tyrosinase, and peroxidase has been studied. The use of a spectrophotometric method and another spectrophotometric chronometric method has made it possible to determine the kinetic parameters Vmax and KM for each enzyme. The highest binding affinity was shown by laccase. The antioxidant capacities of these two molecules have been characterized, finding a very similar primary antioxidant capacity between them. Docking studies revealed the optimal binding position, which was the same for the two molecules and was a catalytically active position. Practical applications: One of the biggest environmental problems in the food industry comes from olive oil mill wastewater with a quantity of approximately 30 million tons per year worldwide. In addition, olive pomace, the solid residue obtained from the olive oil production, is rich in hydroxytyrosol and oleuropein and the action of enzymatic oxidases can give rise to products in their reactions that can lead to polymerization. This polymerization can have beneficial effects because it can increase the antioxidant capacity with potential application on new functional foods or as feed ingredients. Tyrosinase, peroxidase, and laccase are the enzymes degrading these important polyphenols. The application of a spectrophotometric method for laccase and a chronometric method, for tyrosinase and peroxidase, allowed us to obtain the kinetic information of their reactions on hydroxytyrosol and oleuropein. The kinetic information obtained could advance in the understanding of the mechanism of these important industrial enzymes

    Kinetic characterization of the oxidation of catecolamines and related compounds by laccase

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    The pathways of melanization and sclerotization of the cuticle in insects are carried out by the action of laccases on dopamine and related compounds. In this work, the laccase action of Trametes versicolor (TvL) on catecholamines and related compounds has been kinetically characterized. Among them, dopamine, L-dopa, L-epinephrine, L-norepinephrine, DL-isoprenaline, L-isoprenaline, DL-α-methyldopa, L-α-methyldopa and L-dopa methylester. A chronometric method has been used, which is based on measuring the lag period necessary to consume a small amount of ascorbic acid, added to the reaction medium. The use of TvL has allowed docking studies of these molecules to be carried out at the active site of this enzyme. The hydrogen bridge interaction between the hydroxyl oxygen at C-4 with His-458, and with the acid group of Asp-206, would make it possible to transfer the electron to the T1 Cu-(II) copper centre of the enzyme. Furthermore, Phe-265 would facilitate the adaptation of the substrate to the enzyme through Π-Π interactions. To kinetically characterize these compounds, we need to take into consideration that, excluding L-dopa, L-α-methyldopa and DL-α-methyldopa, all compounds are in hydrochloride form. Because of this, first we need to kinetically characterize the inhibition by chloride and, after that, calculate the kinetic parameters K M and V max S. From the kinetic data obtained, it appears that the best substrate is dopamine. The presence of an isopropyl group bound to nitrogen (isoprenaline) makes it especially difficult to catalyse. The formation of the ester (L-dopa methyl ester) practically does not affect catalysis. The addition of a methyl group (α-methyl dopa) increases the rate but decreases the affinity for catalysis. L-Epinephrine and L-norepinephrine have an affinity similar to isoprenaline, but faster catalysis, probably due to the greater nucleophilic power of their phenolic hydroxyl

    Estimation of Diagnosis and Recommendation Integrated System (DRIS), Compositional Nutrient Diagnosis (CND) and Range of Normality (RN) Norms for Mineral Diagnosis of Almonds Trees in Spain

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    To ensure good fertilization, it is necessary to know the optimum nutrient levels for each crop. The most common method for obtaining this information for almond trees is to perform a foliar analysis coupled with the use of interpretive tools such as the traditional range of normality. However, currently, there are other, more sophisticated methods such as the DRIS (Diagnosis and Recommendation Integrated System) and the CND (Compositional Nutrient Diagnosis) which take into account the relationship between nutrients. However, little information is available with respect to these methods in the case of almond trees. In the present work, 288 samples of three contrasting varieties of almond were analyzed—Ferraduel, Ferragnes, and Garrigues (Prunus dulcis, Mill.)— corresponding to bi-weekly sampling between the months of May and September. Leaf analysis data, run with different mathematical and statistical models, lead to knowledge of the optimum period for harvesting samples and the determination of the ranges of normality and norms of DRIS and CND for the Ferraduel, Ferragnes, and Garrigues varieties. Data gained from the leaf nutrient content reported that the best season to harvest and interpret leaf samples was July. In addition, Ferraduel and Ferragnes had higher N, P, and K (2.22, 0.14, and 1.04 mg Kg1 dw, respectively) than Garrigues (2.00, 0.09. 0.67 mg Kg1 dw). The norms obtained with the leaf mineral data showed similar values between the Ferraduel and Ferragnes varieties but different values for Garrigues variety. Therefore, Garriges had the highest N/P, N/K, P/K, and P Mg norms in the DRIS method and the highest VN and VCa norms in the CND method
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