bluuebunny/crossref_metadata_2025_split huggingface dataset:
A NuSTAR Observation of the Low-mass X-Ray Binary GX 349+2 throughout the Z-track
Authors: Coughenour Benjamin M. , Cackett Edward M. , Miller Jon M. , Ludlam Renee M. 
Published: October 2018

Abstract
Although the most luminous class of neutron star (NS) low-mass X-ray binaries, known as Z sources, have been well studied, their behavior is not fully understood. In particular, what causes these sources to trace out the characteristic Z-shaped pattern on color–color or hardness–intensity diagrams (HIDs) is not well known. By studying the physical properties of the different spectral states of these sources, we may better understand such variability. With that goal in mind, we present a recent NuSTAR observation of the Z source GX 349+2, which spans approximately 2 days and covers all its spectral states. By creating an HID we were able to extract five spectra and trace the change in spectral parameters throughout the Z-track. GX 349+2 shows a strong, broad Fe Kα line in all states, regardless of the continuum model used. Through modeling of the reflection spectrum and Fe Kα line we find that in most states the inner disk radius is consistent with remaining unchanged at an average radius of 17.5 R

g
or 36.4 km for a canonical 1.4 M
⊙ NS. During the brightest flaring branch, however, the inner disk radius from reflection is not well constrained.
The Reacceleration of the Shock Wave in the Radio Remnant of SN 1987A
Authors: Cendes Y. , Gaensler B. M. , Ng C.-Y. , Zanardo G. , Staveley-Smith L. , Tzioumis A. K. 
Published: October 2018

Abstract
We report on updated radio imaging observations of the radio remnant of SN 1987A at 9 GHz, taken with the Australia Telescope Compact Array (ATCA), covering a 25 yr period (1992–2017). We use Fourier modeling of the supernova remnant to model its morphology, using both a torus model and a ring model, and find that both models show an increasing flux density and have shown a continuing expansion of the remnant. As found in previous studies, we find that the torus model most accurately fits our data and has shown a change in the remnant expansion at day 9300 ± 210 from 2300 ± 200 km s−1 to 3610 ± 240 km s−1. We have also seen an increase in brightness in the western lobe of the remnant, although the eastern lobe is still the dominant source of emission, unlike what has been observed at contemporary optical and X-ray wavelengths. We expect to observe a reversal in this asymmetry by the year ∼2020, and we note that the southeastern side of the remnant is now beginning to fade, as has also been seen in optical and X-ray data. Our data indicate that high-latitude emission has been present in the remnant from the earliest stages of the shock wave interacting with the equatorial ring around day 5000. However, we find that the emission has become increasingly dominated by the low-lying regions by day 9300, overlapping with the regions of X-ray emission. We conclude that the shock wave is now leaving the equatorial ring, exiting first from the southeast region of the remnant, and is reaccelerating as it begins to interact with the circumstellar medium beyond the dense inner ring.
X-Ray Reverberation Mapping and Dramatic Variability of Seyfert 1 Galaxy 1H 1934-063
Authors: Frederick Sara , Kara Erin , Reynolds Christopher , Pinto Ciro , Fabian Andrew 
Published: October 2018

Abstract
A fraction of active galactic nuclei (AGN) exhibit dramatic variability, which is observed on timescales down to minutes in the X-ray band. We introduce the case study of 1H 1934-063 (z = 0.0102), a Narrow-line Seyfert 1 among the brightest and most variable AGN ever observed with XMM-Newton. This work includes spectral and temporal analyses of a concurrent XMM-Newton and NuSTAR 2015 observation lasting 130 kiloseconds, during which the X-ray source exhibited a steep (factor of ∼6) plummet and subsequent full recovery of the flux level, accompanied by deviation from a single log-normal flux distribution. We rule out Compton-thin obscuration as the cause for this dramatic variability observed even at NuSTAR energies. In order to constrain coronal geometry, dynamics, and emission/absorption processes, we compare a detailed spectral fitting with a Fourier-based timing analysis. Similar to other well-studied, highly variable Seyfert 1s, this AGN is X-ray bright and displays strong reflection features. We find a narrower broad iron line component compared to most Seyfert 1s, and constrain the black hole spin to be <0.1, one of the lowest yet discovered for such systems. Combined spectral and timing results are consistent with a dramatic change in the continuum on timescales as short as a few kiloseconds dictating the nature of this variability. We also discover a Fe–K time lag, measuring a delay of 20 s between relativistically blurred reflection off the inner accretion flow and the hard X-ray continuum emission.
Systematic Investigation of X-Ray Spectral Variability of TeV Blazars during Flares in the RXTE Era
Authors: Wang Yijun , Xue Yongquan , Zhu Shifu , Fan Junhui 
Published: October 2018

Abstract
Utilizing all the 16 yr RXTE observations, we analyze the X-ray spectra of 32 TeV blazars and perform a systematic investigation of X-ray spectral variability for the five brightest sources during their major flares that lasted several days. We obtain photon spectral index (α), flux and synchrotron radiation peak energy (E
p) from empirical spectral fitting, and electron spectral index (p) from theoretical synchrotron radiation modeling. We find that both α and p generally display a harder-when-brighter trend, confirming the results of many previous works. Furthermore, we confirm and strengthen the result that p must vary in order to explain the observed X-ray spectral variability during flares, which would have useful implications for interpreting the associated higher-energy spectral variability. We see apparent electron spectral hysteresis in many but not all p-flux plots that takes a form of “loop” or oblique “8.” We obtain a tight p–hardness ratio (HR) relation and a tighter p–α relation using spectra of flaring periods, both of which are also applicable to stacked data of quiescent periods. We demonstrate that these two empirical relations can be used efficiently to estimate p from HR or α that is readily achieved. Finally, we find that, when considering TeV blazars as a whole, α and X-ray luminosity are positively correlated, E
p is negatively correlated with p and α, and E
p is positively correlated with HR; all these correlations are in line with the blazar sequence. However, after correcting for the Doppler boosting effect, α and intrinsic X-ray luminosity follow an anticorrelation.
The Effect of Vascular Graft and Human Umbilical Cord Blood-Derived CD34+ Stem Cell on Peripheral Nerve Healing
Authors: Yilmaz Ali , Topcu Abdullah , Erdogan Cagdas , Sahin Barbaros , Abban Gulcin , Coskun Erdal , Ozkul Ayca 
Published: October 2018

AIM: There are many trials concerning peripheral nerve damage causes and treatment options. Unfortunately, nerve damage is still a major problem regarding health, social and economic issues. On this study, we used vascular graft and human cord blood derived stem cells to find an alternative treatment solution to this problem.
MATERIAL AND METHODS: We used 21 female Wistar rats on our study. They were anesthetized with ketamine and we studied right hind limbs. On Group 1, we did a full layer cut on the right sciatic nerve. On Group 2, we did a full layer cut on the right sciatic nerve, and we covered synthetic vascular graft on cut area. On Group 3, we did a full layer cut on right sciatic nerve, and we covered the area with stem cell applied vascular graft.
RESULTS: At the end of postoperative 8. weeks, we performed EMG on the rats. When we compared healthy and degenerated areas as a result of EMG, we found significant amplitude differences between the groups on healthy areas whereas there was no significant difference on degenerated areas between the groups. Then we re-opened the operated area again to reveal the sciatic nerve cut area, and we performed electron microscope evaluation. On the stem cell group, we observed that both the axon and the myelin sheet prevented degeneration.
CONCLUSION: This study is a first on using synthetic vascular graft and cord blood derived CD34+ cells in peripheral nerve degeneration. On the tissues that were examined with electron microscope, we observed that CD34+ cells prevented both axonal and myelin sheath degeneration. Nerve tissue showed similar results to the control group, and the damage was minimal.
Changes in bee community structure (Hymenoptera, Apoidea) under three different land-use conditions
Authors: Razo-León Alvaro E. , Vásquez-Bolaños Miguel , Muñoz-Urias Alejandro , Huerta-Martínez Francisco M. 
Published: October 2018

Bee communities were studied with three different conditions of land-use: 1) urban area; 2) crops and livestock; and, 3) preserved vegetation. All three conditions have elements of tropical dry forest and are in the "Sierra de Quila" Flora and Fauna Protection Area and its influence zone. Sampling was carried out throughout the year (three days per month) for each land-use condition. Bee species and their abundance were registered with the intention of knowing how changes in the vegetation are related to bee community structure (richness, abundance, and α and β diversity).A total of 14,054 individuals from 160 species were registered. A rarefaction analysis, showed that the preserved areas had significantly greater richness and diversity. Beta diversity analysis revealed a species turnover of nearly 32% among each pair of conditions. It is concluded that the changes in land-use negatively affect richness and diversity and causes major changes in species composition of the bee community. For this reason, it is recommended that the protection of the tropical dry forest, both for this study area but also in general for Mexico, is essential to guarantee the conservation of this group of insects, which are required for the reproduction of a great number wild and cultivated plant specie.
Les structures élémentaires de la sociabilité
Authors: Châton Gwendal 
Published: October 2018

Resumé Cet article se donne pour objet les deux séminaires de R. Aron, le premier s’étant tenu à la Sorbonne entre 1956 et 1967, le second à l’EPHE entre 1968 et 1977. Dans une perspective consistant à étudier le libéralisme « par le bas », il cherche à rendre compte de la formation d’une mouvance aronienne qui fédère derrière une étiquette libérale un groupe d’intellectuels venus d’horizons divers. Ce processus ne se comprend qu’en opérant une contextualisation de ces séminaires, le premier prenant place dans un moment académique de la trajectoire d’Aron, le second se déployant dans un moment plus politique de celle-ci. La césure entre les deux correspond, sur le plan académique, à la démission d’Aron de la Sorbonne, et au plan politique, à Mai 1968. Cette mouvance portera deux revues, Contrepoint et Commentaire , ayant joué un rôle dans le « tournant antitotalitaire », tout autant qu’elle sera portée par elles.
Facility Side-Tracking for Iceberg Risk Management
Authors: King Tony 
Published: October 2018

Abstract
Currently, iceberg risk mitigation at production facilities in shallower waters (80 to 120 m) on the Grand Banks off the coast of Newfoundland and Labrador is accomplished using iceberg surveillance, towing, water cannons and, in the case of floating facilities, disconnection. Future developments in deeper waters such as the Flemish Pass or the Orphan Basin may be able to utilize compliant mooring and riser systems to allow a floating facility to simply move out of the path of an approaching iceberg without disconnecting. The analysis described here shows that, using simple extrapolation of the observed iceberg trajectory, the risk mitigation provided by facility side-tracking is comparable to existing physical management techniques (iceberg towing and water cannons). Improved short-term iceberg drift forecasting would allow further risk mitigation.
An Icevaning Control for Dynamic Positioning in Managed Ice Condition
Authors: Kim Young-Shik , Kim Jinwhan , Kang Kuk-Jin 
Published: October 2018

Abstract
The presence of sea ice is the primary challenge for marine operations in the Arctic region. It is widely accepted that offshore structures running in the Arctic condition need station-keeping methods as well as ice management actions by icebreakers. Dynamic positioning (DP) is one of the station-keeping methods that can provide mobility and flexibility in marine operations. The presence of sea ice adds complex external forces and moments on the vessel which must be managed by the DP system. This paper presents an icevaning control algorithm of the Arctic DP system. To make the icevaning action of the Arctic offshore vessels without any measurements and estimation of the ice condition including ice drifting, a task space and a null space are defined in the vessel model, and the control law is formulated in the task space. A backstepping technique is utilized to handle the nonlinearity of the Arctic offshore vessel's dynamic model, and the Lyapunov stability theory is applied to guarantee the stability of the proposed icevaning control algorithm. A set of experimental tests are conducted in the ice tank of the Korea Research Institute of Ships and Ocean Engineering to examine the practical feasibility of the proposed icevaning control algorithm.
Propulsion System Ice Load Measurements Onboard IB Polaris
Authors: Maattanen Pirjo , Hanninen Samuli , Heideman Torsten 
Published: October 2018

Abstract
This paper presents operational experience and ice measurement results from Finnish Icebreaker Polaris propulsion system. Icebreaker Polaris applies a novel three propulsion unit concept. During the shipbuilding period an extensive ice load measurement system was installed on two of the Azipod units. The paper will present key findings from the measurements from the winter periods 2017-2018.
The target of the ice load measurement campaign is to increase the designer knowledge of propulsor ice loads in different ship operations. The purpose is to understand in more detail the load distribution for component life estimations and clarify differences between bow and stern propulsor ice loads and frequencies. Due to non-linear load distribution in propulsor at extreme loads, strain gauges were installed at two levels in propulsor hull.
This paper will highlight some measurement results of propulsion system behavior during the ice trials and long term measurements from the winters 2017 and 2018. The full-scale ice operation data collected in the Baltic Sea ice conditions can be further utilized in a development vessel and its propulsion system of heavy polar icebreaker type.
The measurement campaign onboard the Polaris is planned to continue during coming winters. The aim is to collect statistical ice load data to improve the understanding of the fatigue and ultimate design loads. One of the goals is also to clarify how much load the bow mounted propulsion unit will experience compared to the stern units. Based on the measurement results so far, we can conclude that icebreaker with bow mounted Azipod propulsor can be operated without limitations in all ice conditions, just like all the other icebreakers in the Baltic.
Finite Element Analysis of Flexible Pipe Tension Loads Due to Iceberg Interaction
Authors: Pike Kenton , Blundon Andrew 
Published: October 2018

Abstract
Offshore Newfoundland and Labrador, Canada, development costs associated with iceberg protection pose significant challenges in terms of project execution and economics for marginal field subsea tie-backs. The current standard practice is to assume that if an iceberg makes contact with a subsea flowline, the flowline is dragged indefinitely imparting significant load to the connections at each end. To isolate flowlines from downstream and upstream assets, weak links are installed in the flowline that are designed to separate once a specified level of tension is reached. This prevents damage to wellheads and other subsea equipment and eliminates the possibility of uncontrolled hydrocarbon release. However, the weak links are very costly and possess inherent risk of failure, which can lead to an uncontrolled release of hydrocarbons. This paper addresses the requirement of weak links by analyzing the flowline tensions transmitted due to iceberg-flowline-soil interaction events.
The assumption that an iceberg drags a flowline indefinetly imparting significant tension on the end connections can be challenged. This paper seeks to estimate the tension loads developed in an untrenched flexible flowline due to interaction with free-floating and gouging icebergs. Large deformation finite element analysis is utilized to simulate the iceberg-flowline-soil interaction scenario. The iceberg keel is idealized with shape and dimensions based on analysis of recent iceberg profiles. A sensitivity study is conducted to assess the influence of keel size, gouge width and depth on flowline tension developed throughout the flowline resting on very dense sand. The sand constitutive behavior is modelled using a user subroutine accounting for the effects of mean effective stress and relative density on the soil strength and volumetric response.
The ice-flowline-soil interaction mechanisms are detailed for free-floating and gouging interaction events. During interaction with free-floating icebergs, the flowline is typically depressed into the seabed, and the keel rides over the flowline. The gouging interaction scenario simulates the complex interaction between the frontal soil mound developed during the gouging process and the untrenched flowline.
This paper provides new insight into the iceberg-flowline-soil interaction scenario that has not been examined previously. Based on the analysis results presented, an alternative strategy to mitigate tension transfer to downstream and upstream assets is discussed.
Potential Impacts of Seabed 2030 on Arctic Resource Development
Authors: Millar David , Jakobsson Martin 
Published: October 2018

AbstractThe world's oceans are critical to sustaining life, controlling climate, and providing economic wealth. Despite this fact, our understanding of the ocean and its seafloor processes is limited, in part because we lack accurate ocean mapping data. The situation is dramatic in the Arctic, where the physical environment is changing rapidly and where the vast majority of the 15,588,000-square-kilometer Arctic Ocean remains unmapped using modern survey methods. Given current and anticipated increases in vessel traffic, resource exploration and development, and impacts of climate change on coastal areas, the need for bathymetric data in the region is becoming increasingly urgent.The Nippon Foundation-GEBCO Seabed 2030 Project promises a solution for the Arctic's growing data demand. Launched in 2017, the project aims to produce a definitive and publicly available high-resolution map of the world's ocean floor by 2030. To achieve these goals, the program is advancing three strategies. First, existing data must be identified and the remaining gaps mapped. For the Arctic, apart from the ice covered central basin, an appreciable volume of bathymetric data already exists, but the national governments and private sector companies who hold these data will need to make them available to Seabed 2030, even if at decimated levels. Second, the project looks to crowd sourced bathymetry as an important means of acquiring new datasets. Vessels operating in or passing through Arctic waters can log and contribute bathymetric data from their movements. Finally, even if existing data and crowd sourced bathymetry data contributions are made, there will undoubtedly be a need for a coordinated Arctic Ocean basin mapping campaign by a combination of government, scientific, and private industry survey vessels to fill the remaining gaps in coverage.This paper will review the need for bathymetric data in the Arctic, the potential for the Seabed 2030 project to deliver these data, and the methods that will be used to ensure its success. It will also discuss the anticipated impacts of Seabed 2030 on Arctic resource development.
The Challenges of Arctic for Oil and Gas Pipeline Design
Authors: Al-Showaiter Aiman , Fan Chengye , Abdalla Basel , McKinnon Colin 
Published: October 2018

Abstract
It has been discussed that about a quarter of the world untapped oil and gas reserves are located in the Arctic. Development of such prospects has faced challenges, both operational and design-related. Operational challenges include geographic location and associated working conditions, such as remoteness, prolonged darkness, communications and equipment reliability; climate conditions, such as low temperatures and ice coverage; unique characteristics of arctic development, such as high reliability requirements and extremely long tie-backs; and environmental conditions and regulations due to the extremely sensitive Arctic ecosystem. The design related challenges include design conditions, loadings and material issues that are unique to the area and environment and that arise from unique arctic operational and environmental conditions.
Due to those challenges, the design of pipelines in the Arctic area requires the consideration of design conditions that do not apply elsewhere, such as ice gouging, frost heave and permafrost. Advanced numerical analysis is apt to play an important role in addressing these challenges and to bridge the technology gaps that still exist in order to enable optimized developments to proceed.
This paper opens with a review of the main arctic challenges for pipeline design followed by the benefits of using advanced numerical techniques to address problems relevant to the design of pipeline in the arctic environment.