bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of C-glycosyl phosphonate derivatives of 4-amino-4-deoxy-α-L-arabinose
Authors: Kerner Lukáš , Kosma Paul 
Published: October 2019

Incorporation of basic substituents into the structurally conserved domains of cell-wall lipopolysaccharides has been identified as a major mechanism contributing to antimicrobial resistance of Gram-negative pathogenic bacteria. Inhibition of the corresponding enzymatic steps, specifically the transfer of 4-amino-4-deoxy-L-arabinose would thus restore the activity of cationic antimicrobial peptides and several antimicrobial drugs. C-glycosidically linked phospholipid derivatives of 4-amino-4-deoxy-L-arabinose have been prepared as hydrolytically stable and chain-shortened analogues of the native undecaprenyldonor. The C-phosphonate unit was installed via a Wittig-type reaction of benzyl-protected 1,5-arabinonic acid lactone with the lithium salt of dimethyl methylphosphonate followed by an elimination step of the resulting hemiketal leading to the corresponding exo- and endo-glycal derivatives. The ensuing selective mono-demethylation and hydrogenolysis of the benzyl groups and reduction of the 4-azido group gave the α-L-anomeric arabino- and ribo-configured methyl phosphonate esters. In addition, the monomethyl phosphonate glycal intermediates were converted into n-octyl derivatives followed by subsequent selective removal of the methyl phosphonate ester group and hydrogenation to give the octyl-phosphono derivatives. These intermediates thus will be of value for future conversion into transition state analogues as well as for introduction of various lipid extensions at the anomeric phosphonate moiety.
Characteristic Variability Timescales in the Gamma-Ray Power Spectra of Blazars
Authors: Ryan J. L. , Siemiginowska A. , Sobolewska M. A. , Grindlay J. 
Published: October 2019

Abstract
Characteristic variability timescales in blazar γ-ray light curves can provide insights into the physical processes responsible for γ-ray variability. The power spectral density (PSD) is capable of revealing such timescales, which may appear as breaks or periodicities. Continuous-time autoregressive moving-average (CARMA) models can be used to accurately estimate a light curve’s PSD. Through a light-curve simulation study, we develop a methodology to identify PSD breaks using CARMA models. Using this methodology, we study the γ-ray light curves of 13 bright blazars observed with the Fermi Large Area Telescope in the 0.1–300 GeV band over 9.5 yr. We present the blazar γ-ray PSDs, which provide evidence for low-frequency breaks on timescales ∼1 yr in four sources, and an additional high-frequency break on a timescale ∼9 days in one source.
A Quasi-static Hyper-resistive Model of Ultra-high-energy Cosmic-ray Acceleration by Magnetically Collimated Jets Created by Active Galactic Nuclei
Authors: Fowler T. Kenneth , Li Hui , Anantua Richard 
Published: October 2019

Abstract
This is the fourth in a series of companion papers showing that when an efficient dynamo can be maintained by accretion disks around supermassive black holes in active galactic nuclei, it will lead to the formation of a powerful, magnetically collimated helix that could explain the observed jet/radiolobe structures on very large scales. Here, we present a hyper-resistive kinetic theory that shows how different instabilities can cause the slowly evolving magnetically collimated jets to accelerate ions and electrons in different regions of jets and lobes. In particular, we propose that the Drift Cyclotron Loss Cone instability at the ends of jets can accelerate ions up to the observed ultra-high-energy cosmic rays with energies ≈1020 eV. Based on this jet/lobe structure model and its associated acceleration processes, we estimate cosmic-ray intensities and likely radiative signatures and compare them with observations.
Probing the Survival of Planetary Systems in Globular Clusters with Tidal Disruption Events
Authors: Kremer Kyle , D’Orazio Daniel J. , Samsing Johan , Chatterjee Sourav , Rasio Frederic A. 
Published: October 2019

Abstract
Among the growing list of confirmed exoplanets, the number of planets identified in dense star clusters remains sparse. Previous analyses have suggested that this may be due in part to dynamical interactions that can unbind planets from their host stars, limiting the survival of planetary systems in clusters. Thus, alternative detection strategies may be necessary to study planets in clusters that may no longer be bound to a host. Here, we use N-body models to explore the evolution of planetary systems in dense star clusters. Depending on various initial conditions, we show that 10%–50% of primordial planetary systems are broken through dynamical encounters over a cluster’s full lifetime, populating clusters with “free-floating” planets. Furthermore, a large number (30%–80%) of planets are ejected from their host cluster through strong dynamical encounters and/or tidal loss. Additionally, we show that planets naturally mix with stellar-mass black holes (BHs) in the cores of their host cluster. As a consequence, up to a few hundred planets will be tidally disrupted through close passages of BHs. We show that these BH–planet tidal disruption events (TDEs) occur in clusters at a rate of up to 10−5 yr−1 in a Milky-Way-type galaxy. In principle, these BH–planet TDEs may be detected by upcoming transient surveys such as the Large Synoptic Survey Telescope at a rate of a few events per year, although identification of these events may prove challenging. The observed rate of BH–planet TDEs could place new constraints upon the formation and survival of planetary systems and BHs in dense star clusters.
Populations of Stellar-mass Black Holes from Binary Systems
Authors: Wiktorowicz Grzegorz , Wyrzykowski Łukasz , Chruslinska Martyna , Klencki Jakub , Rybicki Krzysztof A. , Belczynski Krzysztof 
Published: October 2019

Abstract
In large and complicated stellar systems like galaxies, it is difficult to predict the number and characteristics of a black hole (BH) population. Such populations may be modeled as an aggregation of homogeneous (i.e., having uniform star formation history and the same initial chemical composition) stellar populations. Using realistic evolutionary models, we predict the abundances and properties of BHs formed from binaries in these environments. We show that the BH population will be dominated by single BHs originating from binary disruptions and stellar mergers. Furthermore, we discuss how BH populations are influenced by such factors as initial parameters, metallicity, initial mass function, and natal kick models. As an example application of our results, we estimate that about 26 microlensing events happen every year in the direction of the Galactic Bulge due to BHs in a survey like OGLE-IV. Our results may be used to perform in-depth studies related to realistic BH populations, such as observational predictions for space survey missions like Gaia or Einstein Probe. We prepared a publicly available database with the raw data from our simulations to be used for more in-depth studies.
Qui reste à la maison ? Organisation du travail rémunéré et des congés après une naissance au sein des couples bi-actifs en Belgique
Authors: Wood Jonas , Marynissen Leen 
Published: October 2019

Bien que les pays occidentaux aient connu un développement sans précédent du modèle des couples à double revenu, l’égalité entre les hommes et les femmes sur le marché du travail reste insuffisante : la division du travail rémunéré entre les sexes continue d’être inégale après les naissances, et les congés parentaux sont très largement pris par les mères. À l’aide de données de panel basées sur des registres belges pour la période 1999-2010, nous évaluons l’influence des caractéristiques d’emploi relatives des conjoints avant l’arrivée d’un enfant sur les situations d’emploi et de prise de congé après la naissance. Les résultats des modèles logit multinomiaux soutiennent l’hypothèse microéconomique selon laquelle le membre du couple ayant le salaire le plus élevé, la plus longue expérience, et réalisant le plus d’heures de travail avant la naissance a le moins de probabilité de quitter le marché du travail. Peu d’éléments étayent l’hypothèse selon laquelle les modalités sexospécifiques des prises de congés seraient liées à des coûts d’opportunité moins élevés des conjoints ayant des salaires plus faibles ou un accès plus facile aux congés parentaux. Enfin, les simulations indiquent qu’au niveau macro, l’impact des caractéristiques d’emploi avant la naissance n’est pas assez fort pour aller au-delà des inégalités de genre post-naissance, particulièrement pour le recours au congé parental qui reste fortement lié aux normes sexuées et aux institutions.
Flexible Joint Stiffness Modelling Improving Ultra Deep Water Rigid Risers Fatigue Damage
Authors: Venero Germain , Gomes Victor , Corrignan Hugues , Carneiro Daniel 
Published: October 2019

Abstract
Fatigue is one of the key governing conditions in the design of rigid risers, in particular those in ultra-deep water. One effective way of improving fatigue is to adopt a lazy wave configuration, rather than a simple catenary. Steel Lazy Wave Risers (SLWR) have been successfully used offshore Brazil (Hoffman et al. 2010, Oliveira et al. 2017) and in the Gulf of Mexico (Beattie et al. 2013), and have been considered for the North Sea (Felista et al. 2015) and offshore Australia (Vijayaraghavan et al. 2015). Yet, it is probably the most computational-intensive aspect of it. Fatigue analyses require a very large number of load cases to be run, on complex, non-linear models. Methods for simplifying aspects of the analysis are highly desirable, but they must be weighed to provide the required safety levels whilst not introducing uneconomical, overconservative assumptions.
The top first weld is a crucial hotspot, in particular for production SLWRs (Senra et al. 2011). These typically adopt flexible joints (FJ) at the connection to the vessel/platform, and linearization of the FJ stiffness is one of these key simplifications that bring significant value in reducing analysis cost.
This paper describes a method for estimating the characteristic angle used for the linearization, which results in significant stiffness reduction in contrast with the usual, simpler method.
Non-linear FJ stiffness curves are usually available, and they provide stiffness associated to the FJ absolute angle. The FJ stiffness significantly reduces with the angle of rotation. The conventional method adopts the stiffness corresponding to the most likely riser angle – absolute value measured from the static configuration. Conversely, the proposed methodology for estimating the most likely change in angle. As the angles often turn up in alternate angles, the proposed method results in much higher characteristic angle, and hence much lower FJ stiffness. The outcome is significantly less conservative designs, whilst still meeting the same required safety margins.
Libra: Applied Technologies Adding Value to a Giant Ultra Deep Water Pre-salt Field - Santos Basin, Brazil
Authors: Anjos Sylvia M.C. , Passarelli Fabio M. , Wambersie Olivier E. , Lewis Keith , Rovina Paulo Sergio , Coelho Osmond , Martins Mariela , Ribeiro Orlando J. Soares , Fernandes Ricardo A. Rosa , Borges Fernando A. 
Published: October 2019

Abstract
Libra reservoirs are among the most productive in Brazil pre-salt province, with oil columns up to 400 m thick. These heterogeneous carbonate reservoirs contain oil with a relatively high Gas Oil Ratio (GOR) and CO2 levels ranging from 40 to 45% in the associated gas. It is also characterized by sparse occurrences of intrusive and extrusive igneous rock within the pre-salt and post salt horizons, which causes additional challenges for seismic imaging and reservoir architecture modelling. Driven by the challenges and fueled by an innovation spirit, the Libra Consortium have been developing a portfolio of technologies to address those challenges and close the technical and operational gaps, in order to add value by reducing and managing uncertainties, optimizing production and overall improving hydrocarbon recovery. Since Libra development strategy is based on full reinjection of produced gas for CO2 disposal purposes and enhanced oil recovery, gas management and its operational robustness over the full life cycle of the field are key. In this context, a focused and robust technological approach based on applied technology portfolio has been adopted to address the many unique challenges and add value to the project through the implementation of new and innovative solutions as well as technologies over the life cycle of the projects.
Exploratory Potential of the Brazilian Equatorial Margin
Authors: d'Almeida Katia Souza , de Souza Marcos Frederico Farias , de Castro Nathália Oliveira , Vilela Pamela Cardoso , Leggieri Raul Fagundes , Fernandes Regina Freitas , Cardoso Roberta de Albuquerque 
Published: October 2019

Abstract
This regional study proposes a regional evaluation of the petroleum potential of the Brazilian Equatorial Margin (EQM), based on the analysis of exploratory plays, in the geological context of the sedimentary basins that compose it. A methodological approach is adopted where plays are the key geological concept and the Geographic Information System (GIS) is the computational tool. The first step is the mapping of the plays' factors (charge, reservoir and trap systems). Subsequently, using geoprocessing techniques, the segments of the plays' factors (subplays) are qualitatively evaluated for geological favorability knowledge. The knowledge of charge, reservoir and trap elements of each exploratory play allows to observe the prospectivity of the area, despite the limitation of data availability at the exploratory frontier basins that make up the EQM. In this work, we have mapped exploratory superplays associated to the EQM's reservoirs with different characteristics and ages. The greatest chances of hydrocarbon discovery were observed in the central portion of the basins that make up the Brazilian EQM, near the 1,500 m isobath; medium and low chances occured in the rest of the effective basin.
Gimbal Joint Riser: Enabling Free-Hanging and Buoyancy-Free Rigid Risers
Authors: Cruz Ivan Pimentel , Ramiro Andre , Karunakaran Daniel , Nicoletti Frederico , Hepner Gustavo Queiroz , Lemos Luiz , Chiodo Mario , Gouveia Joao Carlos Carvalho 
Published: October 2019

Abstract
The novel ‘Gimbal Joint Riser’ (GJR) device is an invention that allows for a free-hanging riser catenary configuration by providing the functionality of adding a ‘hinge’ or articulation in midway of the riser column. Such mid-length articulation allows that dynamic bending and compression at touchdown zone (TDZ) be reduced enough to get within acceptable design limits, what is not achievable with a traditional steel catenary riser (SCR) connected to a spread-moored FPSO in ultra-deep-water scenarios like Santos Basin in Brazil. The aim of the invention is to offer an economic competitive option to current state-of-the-art solution of applying Steel Lazy Wave Risers (SLWR), by eliminating the need of relatively expensive buoyancy modules. The objective of this paper is to present this new concept and simulations results.
The Branched Steel Catenary Riser Interference Study
Authors: Ogbeifun Michael Achoyamen , Oterkus Selda , Race Julia , Naik Harit , Decnop Eduardo , Moorthy Dakshina , Bhowmik Subrata 
Published: October 2019

Abstract
A novel riser concept is being investigated. This is the branched riser system (BRS) with different configuration types including the branched steel catenary riser (BSCR), the branched steel lazy wave riser (BSLWR) and the branched lazy wave hybrid riser (BLWHR). As part of the design and operational requirement for riser systems, riser interference or clash checks is important especially in cases when risers are positioned closely from each other and the external excitations including hydrodynamic interactions are significant. This paper presents findings from the investigation of the interference response of the branches of the BSCR.
The BSCR, with different half branch angles(β = 0.1deg, 0.5deg and 1deg), are hosted by a floating production system in a water depth of 1500m and subjected to different loading conditions including current loads, vessel offsets, variation in branches’ weight, dynamic loads from ocean wave excitations and drag amplification due to VIV. Under these conditions, the minimum clearance between the BSCR branches were calculated and checked against the minimum clearance requirements.
Results from this study showed that the global displacement responses of the BSCR branches are in tandem with each other for non-VIV scenarios and that the minimum clearances between them satisfy the no-clash criteria. This is due to the close drag-to-apparent-weight (DAW) ratio of the branches. Wave load excitations on the BSCR were observed to cause little changes on the branches’ clearance, even when imposed on a combination of worst static conditions. For ‘lockin’ conditions during VIV, it is found that the transverse vibrational amplitude-to-diameter (A/D) ratio of the branches, which impact amplification on the inline drag force can be different for the two branches. This can result in differential deflection of the branches and higher clash possibilities. Under VIV conditions with the current profile typical of Gulf of Mexico (GoM), the BSCR configuration with half branch angle, β = 0.1deg, was found not to satisfy the interference criteria while the BSCR (β=1deg) survived. This indicates that high half branch angle will be required for the BSCR design under high intensity and shearing current profiles acting on the branches. However, all BSCR configurations with half branch angles (β =0.1deg, 0.5deg and 1deg) were found to satisfy the interference requirement when subjected to constant current profiles (slab currents) and current profile typical of West of Africa (WoA), though slab current profile resulted in very high A/D ratio. These results provide positive indications for continuing investigation of other aspects of the BSCR.
Data Science and Business Intelligence Techniques for Learning from Environmental Accident Analysis for Offshore Oil Fields
Authors: Loretti Rômulo Alves , Da Costa Vitor Felipe Pereira , Memoria Daniel Geraldo De Oliveira , Barbosa Andrezza Neves , Oliveira Helton Luiz Santana , Wegner Issac Rafael , Zank Cristiano Andre Christmann 
Published: October 2019

Abstract
Incorporating data science and business intelligence (BI) techniques as a strategy and tool for improving and evolving process safety for the oil and gas industry is a no-return method that should provide extraordinary gains. The technology is a powerful and necessary partner for the oil industry to overcome the challenges of new frontiers for oil exploration and production. Additionally, this applies to the health, safety, and environmental segment of business because more challenging scenarios imply greater potential risks; therefore, access to information within the appropriate time, clearly, and consistently allows the longevity of business. Digital transformation, helped current activities supported by weak instruments (i.e., spreadsheets, e-mails, etc.) to migrate to a database structure that facilitated the understanding of their real situation within the appropriate time—at macro and micro levels—allowing adequate support for decision-making.
BI tools aided by data science techniques facilitate decision-making, often extracting productive information from content-rich texts. The combination of data science techniques with BI tools enables a full-blown experience for business analysts through new insights, background connections not yet discussed, more professional visualizations, and telling the same or a new story using more complete, and often complex, innovative questions and answers. Answering essential questions for process safety in the oil and gas industry when analyzing environmental accidents, atmospheric dispersions, emissions, leaks, and spills in a structured method (presenting graphically within the context of rigs), multiple views of the problem allow improved management of efforts, which reduces the number of cases. The same concept can be expanded to questions related to injuries, machinery and/or equipment damage, performance, etc.
Automated Supervision of Personal Protective Equipment Usage
Authors: Gessoni Lucas Dalmedico , Gadbem Edgar Vilela , Alves Pedro Gonçalves , Ferreira Matheus Pedroza , de Alcântara André Luís Michels , Fernandes Claudio Santos , Colombo Danilo 
Published: October 2019

Abstract
The workers of many fields must follow strict safety rules, and not complying with them may put these workers into severe danger. Oil and Gas workers are subject to hazards and accidents in their workplace frequently. The use of personal protective equipment (PPE) is of summary importance to professionals who work with heavy-duty machinery or in unsafe environments, reducing the risk of serious injuries or even death. The workers are supposed to wear PPE, some of which are gloves, hardhat, and Steel-Toed Boots, during their activities. However, PPE is commonly misused or unused, incurring the need for recurrent inspection. There is no guarantee that the safety equipment is being used correctly, safely and continuously. These threats to the safety of the workers are increased significantly when they are working offshore due to either the harsh conditions they might be working on or inherent dangers that O&G workplaces can offer to the workers such as machinery and dangerous areas with risk of collision and accidents. Detecting the lack of PPE can prevent injuries during work. For this purpose, we propose a surveillance system solution to automatically analyze video footage and detect oil and gas (O&G) workers who are not using adequate protective equipment. This project developed a multi-step detection system using Deep Learning techniques in a pipeline for monitoring workers through camera images. Being able to detect violations to the established rules is an important step towards reducing the impact of incidents and accidents. Using computer vision, deep neural networks, and video footage, we created a web solution for analyzing the imagery in real-time and issuing alerts when a violation happens. For this specific domain, we accomplished the best results by using YOLOv3 as a person detector in conjunction with the Xception network for classification. We achieved 98% precision for the classification step and 78% precision for the joint solution (detection and classification steps) while running in real-time in an NVIDIA Titan X GPU.