bluuebunny/crossref_metadata_2025 huggingface dataset:
Review: Neuroinflammatory pathways as treatment targets and biomarker candidates in epilepsy: emerging evidence from preclinical and clinical studies
Authors: van Vliet E. A. , Aronica E. , Vezzani A. , Ravizza T.
Published: October 2017

Accumulating evidence indicates an important pathophysiological role of brain inflammation in epilepsy. In this review, we will provide an update of specific inflammatory pathways that have been proposed to be crucial in the underlying molecular mechanisms of epilepsy, including the interleukin‐1 receptor/toll‐like receptor signalling, cyclooxygenase‐2, tumour necrosis factor‐alpha, complement signalling and chemokines. Furthermore, by drawing on evidence from preclinical and clinical studies we will discuss the potential of these signalling pathways targets for novel therapeutic interventions that control drug‐resistant seizures or have disease‐modifying effects. Finally, we will assess the use of these inflammatory pathways as potential biomarkers for the development of epilepsy or to measure the effectiveness of therapeutic interventions.
‘Primordialism’ in nationalism studies: theory or ideology?
Authors: Coakley John
Published: October 2017

For several decades, the field of nationalism studies has seen an extended debate about explanations of nationalism and about the process of nation formation. An impressive set of labels has been coined to describe alternative approaches. One of the theories that has enjoyed unusual longevity is the approach known as primordialism, which stresses the deep historical and cultural roots of nations and nationalism and assumes their quasi‐objective character. This resilience is surprising because of the difficulty of marshalling evidence to support such a theory, and because of the line‐up of critics who dismiss it. This article explores the recent debate about primordialism. It suggests that authentic versions of primordialism are extremely hard to find in the academic literature, and that primordialism may better be viewed as an ingredient in nationalism than as an explanation of nationalism.
Assessing the growth of remote working and its consequences for effort, well‐being and work‐life balance
Authors: Felstead Alan , Henseke Golo
Published: October 2017

This article critically assesses the assumption that more and more work is being detached from place and that this is a ‘win‐win’ for both employers and employees. Based on an analysis of official labour market data, it finds that only one‐third of the increase in remote working can be explained by compositional factors such as movement to the knowledge economy, the growth in flexible employment and organisational responses to the changing demographic make‐up of the employed labour force. This suggests that the detachment of work from place is a growing trend. This article also shows that while remote working is associated with higher organisational commitment, job satisfaction and job‐related well‐being, these benefits come at the cost of work intensification and a greater inability to switch off.
Short‐term intermittent energy restriction interventions for weight management: a systematic review and meta‐analysis
Authors: Harris L. , McGarty A. , Hutchison L. , Ells L. , Hankey C.
Published: October 2017

This systematic review synthesized the available evidence on the effect of short‐term periods of intermittent energy restriction (weekly intermittent energy restriction; ≥7‐d energy restriction) in comparison with usual care (daily continuous energy restriction), in the treatment of overweight and obesity in adults. Six electronic databases were searched from inception to October 2016. Only randomized controlled trials of interventions (≥12 weeks) in adults with overweight and obesity were included. Five studies were included in this review. Weekly intermittent energy restriction periods ranged from an energy intake between 1757 and 6276 kJ/d−1. The mean duration of the interventions was 26 (range 14 to 48) weeks. Meta‐analysis demonstrated no significant difference in weight loss between weekly intermittent energy restriction and continuous energy restriction post‐intervention (weighted mean difference: −1.36 [−3.23, 0.51], p = 0.15) and at follow‐up (weighted mean difference: −0.82 [−3.76, 2.11], p = 0.58). Both interventions achieved comparable weight loss of >5 kg and therefore were associated with clinical benefits to health. The findings support the use of weekly intermittent energy restriction as an alternative option for the treatment of obesity. Currently, there is insufficient evidence to support the long‐term sustainable effects of weekly intermittent energy restriction on weight management.
Importance of anticoagulation and postablation silent cerebral lesions: Subanalyses of REVOLUTION and reMARQable studies
Authors: Grimaldi Massimo , Swarup Vijay , DeVille Brian , Sussman Jonathan , Jaïs Pierre , Gaita Fiorenzo , Duytschaever Mattias , Ng G. Andre , Daoud Emile , Lakkireddy Dhanunjaya (DJ) , Horton Rodney , Wickliffe Andrew , Ellis Christopher , Geller Laszlo
Published: October 2017

Background

Silent cerebral lesions (SCLs) are a potential complication of left atrial radiofrequency ablation (RFA) procedures for paroxysmal atrial fibrillation (PAF). We aimed to compare the incidence of SCLs in patients treated with irrigated RFA multielectrode catheters (nMARQ® Catheter group) and irrigated focal RFA catheters (NAVISTAR® THERMOCOOL® Catheter; TC group) after PAF ablation from subpopulation neurological assessment (SNA) cohorts of the REVOLUTION and reMARQable studies.

Methods

Data from SNA cohorts in the prospective, nonrandomized REVOLUTION study (March 2011–September 2013) and the prospective, randomized, controlled reMARQable study (October 2013–November 2015) were included. The incidence of SCLs was assessed pre‐ and postablation using magnetic resonance imaging. Neurological deficits were assessed using the National Institutes of Health Stroke Scale, modified Rankin Scale, and Montreal Cognitive Assessment.

Results

A total of 37 patients from REVOLUTION and 76 patients from reMARQable were included in the SNA cohort of each study. In the REVOLUTION SNA cohort, the incidence of SCLs was 21.1% (4/19) in the nMARQ® Catheter group and 5.9% (1/17) in the TC group. Findings from REVOLUTION helped inform the reMARQable study protocol's stringent anticoagulation regimen. SCL incidence was subsequently reduced in both groups (nMARQ® Catheter, 7.9%; TC, 3.3%). No permanent neurological deficits were observed.

Conclusion

Adherence to a stringent anticoagulation regimen prior to and during ablation procedures appears to be an important factor in minimizing the risk of SCL.
Combining electromagnetic navigation and 3‐D mapping to reduce fluoroscopy time and achieve optimal CRT response
Authors: Barbero Umberto , Budano Carlo , Golzio Pier Giorgio , Castagno Davide , Gaita Fiorenzo
Published: October 2017

Implantation of cardiac resynchronization therapy (CRT) devices can be challenging, time consuming, and associated with high‐dose x‐ray exposure. We present the technique in which an electromagnetic navigation system (MediGuideTM, St. Jude Medical) and an electroanatomical three‐dimensional mapping system (EnSite NavX, St Jude Medical) are usefully combined for implanting implantable cardioverter defibrillator CRT devices with strong reduction of x‐ray exposure, and for targeting the most delayed regions in the activation maps avoiding scars for optimal CRT response.
A case of electromagnetic interference between HeartMate 3 LVAD and implantable cardioverter defibrillator
Authors: Sehatbakhsh Samineh , Kushnir Alexander , Kabach Mohamad , Kolek Matthew , Chait Robert , Ghumman Waqas
Published: October 2017

Implantable cardioverter defibrillators (ICDs) have been shown to have a significant benefit in reducing sudden cardiac death (SCD) in patients with systolic heart failure. Additionally, cardiac devices as a bridge to transplant or destination therapy are often used in patients with end‐stage systolic heart failure. As a result, most patients with left ventricular assist devices (LVADs) also have an ICD. Here, we present an electromagnetic interference (EMI) between HeartMate 3 LVAD and ICD. This issue might be critical for both electrophysiologists and advanced heart failure cardiologists to understand prior to implantation of ICD/LVADs in these patients.
Signaling Cascades Activated by UVB in Human Melanocytes Lead to the Increased Expression of Melanocyte Receptors, Endothelin B Receptor and c‐KIT
Authors: Terazawa Shuko , Imokawa Genji
Published: October 2017

A single exposure of normal human melanocytes (NHMs) to ultraviolet B (UVB) radiation induces a distinct increase in the expression of c‐KIT and endothelin B receptor (EDNRB) and upregulates the expression of microphthalmia‐associated transcription factor (MITF). In this review, we clarify the signaling mechanisms by which UVB stimulates the expression of MITF in NHMs, thus leading to upregulation of those two important melanogenic receptors. The increased expression of MITF in UVB‐exposed NHMs is accompanied by a markedly stimulated and prolonged phosphorylation of p38/CREB. The UVB‐stimulated expression of c‐KIT and EDNRB could be completely abolished by a p38 inhibitor concomitant with a reduced phosphorylation of CREB and a downregulation of MITF expression. The UVB exposure of NHMs stimulates the phosphorylation of p38 and c‐jun N‐terminal kinase, but not ERK, followed by the increased phosphorylation of MSK1 and subsequently CREB. Postirradiation treatment with the MSK1 inhibitor H89 significantly downregulates the increased mRNA and protein expression of MITF, EDNRB and c‐KIT in UVB‐exposed NHMs. Our findings indicate for the first time that the increased expression of MITF that leads to the upregulation of melanocyte‐specific proteins in UVB‐exposed NHMs is mediated via activation of the p38/MSK1/CREB axis but not the ERK/RSK/CREB axis.
Prevalence and predictors of sunburn among beachgoers
Authors: de Troya‐Martín Magdalena , de Gálvez‐Aranda María Victoria , Rivas‐Ruiz Francisco , Blázquez‐Sánchez Nuria , Fernández‐Morano Maria Teresa , Padilla‐España Laura , Herrera‐Ceballos Enrique
Published: October 2017

Background

Painful sunburns at any age are one of the main risk factors for skin cancer.

Objectives

To determine the prevalence and predictors of sunburn among beachgoers.

Methods

A cross‐sectional health survey was conducted at the beach during the summer. Adults >18 years with an understanding of Spanish were interviewed using a questionnaire about behaviours, attitudes and knowledge related to sun exposure at the beach. A descriptive analysis was performed, and a log‐binomial regression model was used to determine predictors of sunburn.

Results

The survey was completed by 1054 beachgoers, with a mean age of 43.8 (SD: 18.7) years, 61.2% women, skin phototypes i (13.6%), ii (22.3%), iii (34.0%) and iv (30.2%). 46.9% of responders reported at least one painful sunburn during the previous summer. Age, sex, education, skin phototype, midday sun exposure, sun protection habits, attitudes towards tanning and knowledge about skin cancer were identified as independent predictors of sunburn.

Conclusions

It is necessary to develop photoprotection campaigns aimed at beachgoers, particularly in young people, men, those with skin phototypes I‐III and secondary or university education. Educational strategies should be aimed at discouraging sun exposure at midday, changing attitudes towards tanning and improving knowledge about skin cancer.
Extended survival of Puccinia graminis f. sp. tritici urediniospores: implications for biosecurity and on‐farm management
Authors: Barua P. , You M. P. , Bayliss K. L. , Lanoiselet V. , Barbetti M. J.
Published: October 2017

Puccinia graminis f. sp. tritici (Pgt), the causal organism of stem rust, is of global importance across wheat‐growing countries. However, some epidemics commence without the obvious presence of ‘alternate’ or ‘green bridge’ hosts, suggesting urediniospores can survive in the absence of suitable host plants for many weeks. Testing a range of inert material types, including metals, plastics, fabrics and woods, highlighted a significant effect of material type and temperature on urediniospore viability (P < 0.001), with urediniospores remaining attached and viable on these materials (aluminium, paper, rubber, all fabric and all woods) for up to 365 days at 23/8 °C day/night. At 36/14 °C day/night, urediniospore viability was retained for a maximum of 300 days on denim and jute. Furthermore, at 45/15 °C day/night, urediniospores remained viable for a maximum of 180 days on cotton and jute. The frequency of recovery of attached urediniospores was also dependent upon the material type, with significant differences between materials in their abilities to retain urediniospores after washing (P < 0.001). Urediniospores recovered even after 300 or 365 days from the lower two temperature regimes successfully initiated infections of wheat seedlings. Results confirm the potential importance of inert materials as long‐term carriers of viable Pgt urediniospores, highlighting risks of spread of new pathotypes and strains across wheat‐growing regions, the significant biosecurity implications for contaminated carrier materials, and its likely survival across seasons without a host.
A molecular phylogeny of East African Amytta (Orthoptera: Tettigoniidae, Meconematinae) with data on their cytogenetics
Authors: HEMP CLAUDIA , HELLER KLAUS‐GERHARD , WARCHAŁOWSKA‐ŚLIWA ELŻBIETA , GRZYWACZ BEATA
Published: October 2017

This is the first study to address the molecular phylogeny of East African Meconematinae. We used DNA sequence data from the three genes cytochrome oxidase subunit I (COI), 16S rRNA and histone H3 to reconstruct the relationships within the genus Amytta using Bayesian Inference and maximum likelihood. We included 45 individuals representing 19 Meconematinae taxa from Africa, Europe and Australia, and three outgroup species to explore taxonomic limits at different levels. Members of the genus Amytta belong to three related lineages within Meconematinae. Species of Amytta were found to be monophyletic with Meconema and Phlugidia as sister groups. The molecular results are in accordance with previous morphological and ecological studies. Chromosome numbers and the type of sex determination systems found in Amytta agrees with the three lineages also found in the phylogenetic tree. We conclude that the radiation of Amytta species is geological young. Biogeographical patterns caused by climatic fluctuations of the past seen also in other nonrelated Orthoptera taxa such as the coptacrine genus Parepistaurus are the drivers of biodiversity in the area.
Largely additive effects of gibberellin and strigolactone on gene expression in Arabidopsis thaliana seedlings
Authors: Lantzouni Ourania , Klermund Carina , Schwechheimer Claus
Published: October 2017

The phytohormones gibberellin (GA) and strigolactone (SL) are involved in essential processes in plant development. Both GA and SL signal transduction mechanisms employ α/β‐hydrolase‐derived receptors that confer E3 ubiquitin ligase‐mediated protein degradation processes. This suggests a common evolutionary origin of these pathways and possibly a molecular interaction between them. One such indication stems from rice, where the DELLA protein of the GA pathway was reported to interact with the SL receptor. Here, we examine the physiological interaction between both pathways through the analysis of GA (ga1) and SL biosynthesis (max1 and max3) mutants. In ga1 max double mutants, we find indications only for additive interactions when examining several phenotypic readouts. We further identify short‐term transcriptional responses to GA and the synthetic SL rac‐GR24 through next‐generation sequencing of poly‐adenylated RNAs (RNA‐seq) in ga1 max1. Remarkably, both hormones lead to predominantly additive transcriptional changes of a largely overlapping set of genes. The expression of only a few genes was altered in a synergistic manner but, interestingly, these include the genes encoding the GA catabolic enzyme GA2 OXIDASE2 (GA2ox2) as well as the SL pathway regulators BRANCHED1 (BRC1) and SUPPRESSOR OF max2 1‐LIKE8 (SMXL8). We conclude that GA and rac‐GR24 signaling in Arabidopsis seedlings converge at the level of transcription of a common gene‐set.
Multifaceted plant responses to circumvent Phe hyperaccumulation by downregulation of flux through the shikimate pathway and by vacuolar Phe sequestration
Authors: Lynch Joseph H. , Orlova Irina , Zhao Chengsong , Guo Longyun , Jaini Rohit , Maeda Hiroshi , Akhtar Tariq , Cruz‐Lebron Junellie , Rhodes David , Morgan John , Pilot Guillaume , Pichersky Eran , Dudareva Natalia
Published: October 2017

Detrimental effects of hyperaccumulation of the aromatic amino acid phenylalanine (Phe) in animals, known as phenylketonuria, are mitigated by excretion of Phe derivatives; however, how plants endure Phe accumulating conditions in the absence of an excretion system is currently unknown. To achieve Phe hyperaccumulation in a plant system, we simultaneously decreased in petunia flowers expression of all three Phe ammonia lyase (PAL) isoforms that catalyze the non‐oxidative deamination of Phe to trans‐cinnamic acid, the committed step for the major pathway of Phe metabolism. A total decrease in PAL activity by 81–94% led to an 18‐fold expansion of the internal Phe pool. Phe accumulation had multifaceted intercompartmental effects on aromatic amino acid metabolism. It resulted in a decrease in the overall flux through the shikimate pathway, and a redirection of carbon flux toward the shikimate‐derived aromatic amino acids tyrosine and tryptophan. Accumulation of Phe did not lead to an increase in flux toward phenylacetaldehyde, for which Phe is a direct precursor. Metabolic flux analysis revealed this to be due to the presence of a distinct metabolically inactive pool of Phe, likely localized in the vacuole. We have identified a vacuolar cationic amino acid transporter (PhCAT2) that contributes to sequestering excess of Phe in the vacuole. In vitro assays confirmed PhCAT2 can transport Phe, and decreased PhCAT2 expression in PAL‐RNAi transgenic plants resulted in 1.6‐fold increase in phenylacetaldehyde emission. These results demonstrate mechanisms by which plants maintain intercompartmental aromatic amino acid homeostasis, and provide critical insight for future phenylpropanoid metabolic engineering strategies.
Analyses of the Efficiency of a High-Temperature Gas-Cooled Nuclear Reactor Cogeneration System Generating Heat for the Sulfur–Iodine Cycle
Authors: Jędrzejewski Julian , Hanuszkiewicz-Drapała Małgorzata
Published: October 2017

The paper presents the possibilities of the use of a high-temperature gas-cooled nuclear reactor for energy purposes in the hydrogen and electricity production process. The system provides heat for a thermochemical sulfur–iodine cycle producing hydrogen and generates electricity. Its structure and electricity generation capacity are conditioned by the demand for heat and the levels of temperature required at the sulfur–iodine cycle individual stages. In the three structures under analysis, electricity is generated in a gas turbine system and steam systems (steam, low-boiling fluids). The impact of helium parameters in a two-stage compression system with interstage cooling on power efficiency of the analyzed structures of cogeneration systems and on total power efficiency of the systems is investigated assuming that both hydrogen and electricity are produced. Thermodynamic analyses are conducted using the EBSILON Professional program. The aim of the analyses is to determine the optimum structure of the system and parameters of the mediums in terms of power efficiency.
Trio-V Wind Analyzer: A Generic Integral System for Wind Farm Suitability Design and Power Prediction Using Big Data Analytics
Authors: Fawzy Dina , Moussa Sherin , Badr Nagwa
Published: October 2017

A fast-growing worldwide interest is directed toward green energies. Due to the huge costs of wind farms establishment, the location for wind farms should be carefully determined to achieve the optimum return of investment. Consequently, researches have been conducted to investigate land suitability prior to wind plants development. The generated data from the sensors detecting a potential land can be very huge, fast in generation, heterogeneous, and incomplete, which become seriously difficult to process using traditional approaches. In this paper, we propose Trio-V Wind Analyzer (WA) that handles data volume, variety, and veracity to identify the most suitable location for wind energy development in any study area using a modified version of multicriteria evaluation (MCE). It utilizes principal component analysis (PCA) and our proposed Double-Reduction Optimum Apriori (DROA) to analyze most of the environmental, physical, and economical criteria. In addition, Trio-V WA recommends the suitable turbines and proposes the adequate turbines’ layout distribution, predicting the expected power generated based on the recommended turbine’s specifications using a regression technique. Thus, Trio-V WA provides an integral system of land evaluation for potential investment in wind farms. Experiments indicate 80% and 95% average accuracy for land suitability degree and power prediction, respectively, with efficient performance.
Bayesian Estimation of Directional Wave-Spectrum Using Vessel Movements and Wave-Probes: Proposal and Preliminary Experimental Validation
Authors: Souza Felipe Lopes de , Tannuri Eduardo Aoun , de Mello Pedro Cardozo , Franzini Guilherme , Mas-Soler Jordi , Simos Alexandre Nicolaos
Published: October 2017

The measurement of the directional wave spectrum in oceans has been done by different approaches, mainly wave-buoys, satellite imagery and radar technologies; these methods, however, present some inherent drawbacks, e.g., difficult maintenance, low-resolution around areas of interest and high-cost. In order to overcome those problems, recent works in the area proposed a motion-based estimation procedure using the vessel, or the floating facility, as a wave sensor, what was called wave-buoy analogy. Despite of solving the issues, the solution is still incomplete, since it suffers from low estimation capabilities of the spectral energy below the cut-off period of the systems, around eight seconds, a frequency range that is responsible for the drift effects, that are critical for operation planning and dynamic positioning. This work studies the usage of wave-probes installed on the hull of a moored vessel to enhance the estimation capabilities of the motion-based strategy, using a high-order estimation method based on Bayesian statistics. The proposal is founded on the asymptotical response of the oceanic systems facing low period waves, which starts to behave like a wall, reflecting all the incoming energy, i.e., the worst the motion-based estimation is, the better the wave-elevation based estimation should be. Firstly, the measurements from the wave-probes are incorporated to the dynamic system of the vessel as new degrees-of-freedom, using a linear model extension, thus the Bayesian method can be expanded without additional reasoning. Secondly, the linear model hypothesis and the possible improvements are validated by experiments conducted in a wave-basin with a scale model of a moored FPSO-VLCC, concluding that the approach is able to improve not only the estimation of spectra with low peak period, but also the estimation in the entire range of expected spectra, mainly the significant height and the peak period properties. Lastly, some drawbacks are discussed, as the effect of the non-linear roll movement, which must be taken in account when calculating the wave-probe response; and the poor mean-direction estimation capability in some particular wave directions and low peak periods, in which even the vessel motions allied with the wave-probe response are not able to provide the proper direction discrimination.
Moonpool Behavior of a Stationary Vessel in Waves and a Method to Increase Operability
Authors: Chalkias Dimitris , Krijger Jan-Willem
Published: October 2017

Potential flow frequency domain calculations have been performed to predict the natural frequencies and water motions for several moonpools. The moonpool free surface has been replaced by a damping lid in WAMIT without changing the kinematic free surface condition. Instead, the free surface modes of motion have been modeled as generalized modes. In this way, different damping values per mode can be applied. Damping values have been calculated based on CFD free decay tests and validated with model tests.

Two vessels were chosen for this study with different moonpool dimensions and shapes. The first is a construction vessel with a small rectangular moonpool, whereas the second is a drillship featuring a large moonpool optimized for transit. Free decay CFD calculations have been performed for both vessels, while CFD regular wave calculations have been performed for the construction vessel and model tests were performed for the drillship.

Using the aforementioned methodology, a motion reduction device is designed and presented in this paper. The aim of this device is to reduce the motions experienced in the moonpool during vessel operations in a sea state and thus to increase the operability of the vessel with respect to moonpool motion limitations.

The increased vessel operability with the new device is shown by a wave scatter analysis. In order to calculate the workability limit curves, suitable limits have been chosen for the free surface elevation and the water vertical velocity in the moonpool.
Motion Characteristic Analysis of a Floating Structure in the South China Sea Based on Prototype Monitoring
Authors: Wu Wen-hua , Cui Xiao-wei , Lv Bai-cheng , Wang Shi-sheng , Feng Jia-guo , Yue Qian-jin
Published: October 2017

Background: Due to the complexity of ocean environmental loading models, together with the nonlinearity and empirical parameters involved in hydrodynamic numerical modeling and model testing, many uncertainties and challenges still exist in the design and operation of platforms built to float at sea. On-site prototype measurements carried out on actual floating structures provide a valid strategy for obtaining accurate environmental loading parameters and floater motion responses.

Problem definition: A prototype monitoring system has been built as part of a joint industrial project in the South China Sea. A complete set of long-term ocean environment loading parameters and structural dynamic motion responses has been gathered for the period from 2012 to the present. Several advanced techniques, such as the independent remote monitoring technique (IRMT), the integrated continuous measurement technique and the standalone underwater measurement technique were established to enhance the reliability of data collection even during extreme typhoon conditions when there was no power.

Solution approach and findings: this paper analyzes the dynamic motion characteristics of the platform structure based on the monitoring data. The relationship between the measured wave spectrum and the JONSWAP spectrum is discussed. The spectral shape parameters of the JONSWAP spectrum for the South China Sea, as derived from the monitoring data, are discussed. The dynamic motions of the platform structure are analyzed based on artificial neural networks (ANN) using data from a typical monitored typhoon. The numerical modeling used in this research is constructed to perform the identification analysis of the platform parameters using radius basic function (RBF) and hydrodynamic results produced by ANSYS-AQWA. This research selects five main geometric parameters related to the platform design. Mass, moments of inertia of three rotation degrees, and the position of the center of gravity (COG) are selected as the optimization objectives. The mean values of surge and pitch and standard deviations of roll and pitch are treated as the input parameters. Modeling verifications show that the present ANN-based method performs well in obtaining the optimal platform parameters. The maximum error between the simulated and monitored results in terms of the measurement of the roll, pitch, surge and sway motions fall within 5%. The model of the monitored platform could be further updated; it could be made capable of performing the performance assessments of the dynamic characteristics in extreme and/or harsh environmental conditions.
Vortex-Induced Motion of a Free-Standing Riser Below the Critical Mass Ratio
Authors: Florager Curtis , Balash Cheslav
Published: October 2017

The presented work studied the vortex-induced motion (VIM) response of a free-standing riser (FSR) with varied riser length and buoyancy can (BC) mass with an ultimate aim to find a combination that would reduce the motion of the system. Specifically, four model configurations were experimentally tested in a flume tank over a range of flow velocities, with the BC motion recorded by a submersible camera positioned directly above the model; consequently, inline (IL) and crossflow (CF) amplitudes were estimated with a motion tracking software. In the pre-resonant flow regime, non-dimensionally, minimal differences were observed between the CF amplitudes, and the IL motion was reduced with a longer riser. Given the extreme length of full-scale FSRs and inherent low natural frequency, it is impractical to increase the riser tension to a point where VIM would not occur under normal environmental conditions. Alternatively, increasing the mass ratio of the BC so that it is above the critical mass ratio of 0.54 (the ratio of the mass of the body to the mass of the fluid) would limit the resonant flow velocities to a finite range, but a larger BC may not be an economically viable solution, and because of the increased diameter, it would experience a larger CF amplitude during resonance. Further study into the prevention of VIM of an FSR by varying the riser length and BC mass is unlikely to be beneficial.
A Preliminary Assessment of the Use of a Large Semi-Submersible Platform As a Motion-Based Wave Sensor
Authors: Mas-Soler J. , Simos Alexandre N. , de Mello Pedro C. , Tannuri Eduardo A. , Souza Felipe L.
Published: October 2017

A well-known drawback of conventional wave monitoring systems, such as wave buoys, is that they experience a loss of accuracy in extreme wave conditions. Also, most of them require important initial investment and/or high maintenance costs. Over the last few years, directional wave inference obtained from the record of vessel motions is a technique that has significantly grown as complement to traditional methods. This article presents a feasibility study on the use of the motions of a semi-submersible platform for performing wave inference. Experiments were carried out at the USP wave basin (CH-TPN) using a 1:120 scale model of a large semi-submersible platform in operational condition and five different headings. In order to provide an extensive test matrix, the experimental campaign included a set of 32 different irregular waves (sea conditions) for each heading, selected from the scatter diagram of the Norwegian sea and covering many of the sea states of interest for this research. Moreover, each sea condition was obtained using the most appropriate type of energy spectrum (JONSWAP or Torsethaugen). Bayesian inference motion-based method was adapted for the semi-submersible platform by the proper adjustment of the hyper-parameters. The estimations obtained with the Bayesian wave inference method, using the semi-submersible recorded motions, were confronted with the directional wave spectra measured during the calibration process from an array of wave probes. The results attested that the method was able to capture all of the wave conditions tested during the experimental campaign with reasonable accuracy, even the more extreme cases. They suggest that the semisubmersible platform may indeed be a promising alternative for inferring severe sea conditions.
Control of Flow-Induced Motion in Multi-Column Offshore Platform by Near-Wake Jets
Authors: Guan M. Z. , Narendran K. , Miyanawala T. P. , Ma P. F. , Jaiman R. K.
Published: October 2017

Vortex-induced motion (VIM) poses a serious challenge in the design and operation of deep-draft offshore platforms subjected to ocean current flow. The objective of the present work is to investigate the suppression of VIM by blowing jet flows at the wake side of a floating platform. To begin with, we first perform a systematic investigation of 2D four-column configuration with and without steady jet flows at Re = 200 and m* = 1. The numerical investigations are carried out for various jet flow velocity ratios (Vjet/U) ranging from 0 to 1 at reduced velocity Ur = 5. From the 2D studies, we observe approximately 30% reduction of forces and displacements for the system with steady jet flow compared to the system without jet flow. We also investigate the effect of angle of blowing jet flow (θ) on the effectiveness of VIM suppression. The idea of jet implementation is extended to 3D model of single square column. The effects of jet positions at the back surface of the single square column are discussed. From the investigations, it is observed that the jet flows at center portion is more effective than the jets at the corners of the column. Based upon the 2D and 3D studies of canonical configurations, the VIV suppression technique by jet flows is employed in a 3D deep-draft floating platform at Re = 20,000.
Ocean Swell: How Much Do We Know
Authors: Babanin Alexander V. , Jiang Haoyu
Published: October 2017

Swell waves are present in more than 80% of ocean seas, and provide significant adverse impact on maritime operations. Their prediction by wave-forecast models, however, is poor, both in terms of wave amplitude and, particularly, arrival time. The very definition of ocean swell is ambiguous: while it is usually perceived as former wind-generated waves, in fact it may reconnect with the local wind through nonlinear interactions. The paper will bring together an overview of the complex swell problem. The visible swell attenuation is driven by a number of dissipative and non-dissipative processes. The dissipative phenomena include interaction with turbulence on the water and air sides, with adverse winds or currents. Non-dissipative contributions to the gradual decline of wave amplitude come from frequency dispersion, directional spreading, refraction by currents, and lateral diffraction of wave energy. The interactions with local winds/waves can, on the contrary, cause swell growth. Swell arrival time is the least understood and the most uncertain problem. Joint analysis of buoy observations and model reanalysis shows that swell can be tens of hours early or late by comparison with model predictions. Linear and nonlinear effects which can contribute to such biases are discussed.
Estimating Hydrodynamic Sectional Loads for FPSOs Using Artificial Neural Networks
Authors: Engebretsen Espen , Shu Zhi , Borgen Jon Erik
Published: October 2017

Sizing of a new build FPSO hull is an iterative optimization process, where the main dimensions of the FPSO are varied until the optimal size is found, within a defined input domain. A wide range of criteria should be evaluated per size iteration, and thus the sizing process may be a very time consuming task. In order to speed up this process, it may be beneficial to adopt an automated iterative algorithm for performing the sizing of new build FPSOs for the Concept and Front-End Engineering Design (FEED) phase.

The hull steel weight should be calculated for each size iteration, thus the hydrodynamic bending moment and shear force are needed. Obtaining the hydrodynamic sectional loads requires relatively time consuming calculations (compared to e.g. the required hydrostatic calculation), such as linear diffraction/radiation analysis and stochastic postprocessing. The required computational time of the automated sizing algorithm can be significantly reduced by calculating the hydrodynamic sectional loads by a simplified estimator, eliminating the need for e.g. diffraction/radiation analysis. Such an estimator may be obtained by the use of Artificial Neural Networks (ANNs).

This paper presents how to estimate the hydrodynamic vertical bending moment and shear force for FPSOs, within acceptable accuracy to be used for initial sizing, using ANNs. The estimators, i.e. the ANNs, take known inputs such as the main dimensions, draft and pitch radius of gyration of the FPSO. The ANNs are trained on a database containing linear diffraction/radiation analyses for a variety of FPSO main dimensions, hull shapes and loading conditions.

The database has been established by batch processing of the DNV-GL software HydroD [1], Wadam [2] and Postresp [3] through MATLAB [4]. This paper presents the methods used to obtain the results contained in the database, as well as training and performance of the ANNs.
Reliability Analysis of Offshore Structures Using OMA Based Fatigue Stresses
Authors: Nabuco Bruna , Tarpø Marius , Aïssani Amina , Brincker Rune
Published: October 2017

Today, many offshore structures in the North Sea already reached their predicted lifetime. Since it is still required a huge demand of oil, it results in an important need to keep those structures in operation. The great attention concerning the lifetime of offshore platforms has trigged a need for monitoring these structures in order to gain information about their actual state and hence reduce the uncertainty and allow for more optimal decision planning regarding maintenance, repair and future inspection actions.

Throughout the lifetime, the performance of the structure can be evaluated by analyzing the deterioration process of the structure. In the offshore environment, one of the most common deterioration mechanisms is the fatigue of structural steel induced by wave loading. The deterioration formulation of a structural system subjected to fatigue is nowadays well known. However, many uncertainties may affect the accuracy of the performance evaluation. It can be mentioned mainly the uncertainties related to the materials, the uncertainty on Miner’s rule and the uncertainty on the SN curve but most importantly is the uncertainty on the stress ranges induced by the wave loading.

In this paper, the mainly focus is on the uncertainty observed on the different stresses used to predict the damage. This uncertainty can be reduced by Modal Based Fatigue Monitoring which is a technique based on continuously measuring of the accelerations in few points of the structure with the use of accelerometers known as reliable for long time measurements. An Operational Modal Analysis (OMA) is performed and then a modal filtering of the operating response is considered, so that the modal coordinates of all significant modes are known. Next, the experimental mode shapes are expanded using a Finite Element (FE) model together with the Local Correspondence (LC) principle and the displacements can be estimated in all degrees of freedom of the FE model, allowing the stresses and strains to be obtained from the element equations. It is important to emphasize that even though the accelerations are measured in only a few points of the structure, the stress history can be calculated in any arbitrary point of the structure.

The accuracy of the estimated actual stress is analyzed by experimental tests on a scale model where the obtained stresses are compared to strain gauges measurements. After evaluating the fatigue stresses directly from the operational response of the structure, a reliability analysis is performed in order to estimate the reliability of using Modal Based Fatigue Monitoring for long term fatigue studies.
VIV Responses of Riser With Buoyancy Elements: Forced Motion Test and Numerical Prediction
Authors: Wu Jie , Lie Halvor , Fu ShiXiao , Baarholm Rolf , Constantinides Yiannis
Published: October 2017

Steel Lazy Wave Riser (SLWR) is an attractive deep water riser concept. When subjected to vortex induced vibrations (VIV), the vortex shedding process of the buoyancy element and the bare riser section will be different due to the difference in diameter. VIV responses can be strongly influenced by the dimension of the buoyancy element and its arrangement.

Empirical VIV prediction programs, such as VIVANA, SHEAR7 and VIVA, are widely used by the industry for design against VIV loads. However, there is lack of hydrodynamic data to be used in these programs when buoyancy elements are present.

Experiment to obtain hydrodynamic data for riser with staggered buoyancy elements was carried out in the towing tank in SINTEF Ocean. A rigid cylinder section with three staggered buoyancy elements was subjected to harmonic forced cross-flow (CF) motions. Hydrodynamic forces on one of the buoyancy elements were directly measured in addition to the measured forces at both ends of the test section. Two buoyancy element configurations were tested and the corresponding hydrodynamic data are compared with that of a bare cylinder. The obtained hydrodynamic data was also used in VIV prediction software and good prediction against existing flexible cylinder staggered buoyancy element VIV test data was achieved. A roadmap to achieve an optimal SLWR design by combining different experimental and numerical methods is suggested.
Column Slamming Loads on a TLP From Steep and Breaking Waves
Authors: Vestbøstad Tone M. , Økland Ole David , Lian Gunnar , Stavang Terje Peder
Published: October 2017

Previous model test campaigns of various large-volume platforms indicate that wave impact loads on vertical platform columns can become high in extreme sea states. Column slamming is a highly non-linear and complex problem and reliable estimation1 of Ultimate Limit State (ULS) and Accidental Limit State (ALS) design loads is a challenge. Previous measurements indicate ALS pressures of about 3 MPa acting on an area of typically 50m2 in North Sea and Norwegian Sea wave conditions. The corresponding ULS loads were in the range 1.5–2.0 MPa for the same impact area. Such high predictions for ULS and ALS impact pressures may be critical for both steel and concrete platforms, and accurate predictions of design loads is therefore crucial to establish the correct level of safety.

A model test campaign dedicated to investigate column slamming has been performed on the Heidrun platform, a large concrete Tension Leg Platform (TLP). The column diameter is 31 m. The test campaign was performed in 2013 at Marintek (now Sintef Ocean), at a model scale of 1:55. The main objective of the test campaign was to estimate the characteristic slamming loads, defined as the q-annual extreme 3-hour slamming load level of 10−2 for the Ultimate Limit State (ULS) and 10−4 for the Accidental Limit State (ALS).

To ascertain that the test campaign would result in reliable load estimates, a pre-study on column slamming was performed, involving a selected expert group with participants from several organizations. Review of previous work, identification of governing parameters for wave impact and assessment of model uncertainties and extreme value prediction of slamming loads was performed. It was concluded that two challenges were to be specifically addressed during the planning and execution of the test: 1) the localized nature and short duration of the slamming loads and 2) the large statistical variability of the slamming loads. To address the first challenge, special focus was given to the extent and quality of the instrumentation capturing the slamming loads. Comprehensive documentation of the instrumentation was also performed using hammer testing, structural analysis and drop tests. The second challenge was addressed with a carefully planned test strategy. The resulting model test campaign set a new standard for model testing of such loads, using over 80 slamming panels with a sampling frequency of 19.2 kHz, and over 300 sea state realizations.

This paper presents the planning and execution of the model test campaign, including the instrumentation and model set-up, the test matrix, main challenges, findings and results.
Safety of Pipelines Subjected to Deterioration Processes Modelled Through Dynamic Bayesian Networks
Authors: Palencia O. G. , Teixeira A. P. , Guedes Soares C.
Published: October 2017

The paper studies the application of Dynamic Bayesian Networks for modelling degradation processes in oil and gas pipelines. A DBN tool consisting of a Matlab code has been developed for performing inference on models. The tool is then applied for probabilistic modelling of the burst pressure of a pipe subjected to corrosion degradation and for safety assessment. The burst pressure is evaluated using the ASME B31G design method and other empirical formulas. A model for corrosion prediction in pipelines and its governing parameters are explicitly included into the probabilistic framework. Different sets of simulated corrosion measurements are used to increase the accuracy of the model predictions. Several parametric studies are conducted to investigate how changes in the observed corrosion (depth and length) and in the frequency of inspections affect the pipe reliability.
Guidelines for Estimating Remaining Fatigue Life of Ageing Offshore Jacket Structures
Authors: Aeran Ashish , Gudmestad Ove Tobias
Published: October 2017

The majority of offshore installations worldwide are currently operating beyond their design life. There are still plenty of oil reserves left in existing fields and new smaller fields are unprofitable for stand-alone development. It is therefore essential to use the existing infrastructure efficiently. There is a need to estimate the remaining life of ageing installations more precisely. Ageing is generally characterized by fatigue and corrosion. For an accurate estimation of the remaining life, it is important to simulate the past loadings and structural degradation precisely. However, the past loading histories are generally not available. Also, very few guidelines are available for the simulation of structural degradation in the absence of thickness reduction measurements. To address these issues, this paper first presents an overview of the age profile of fixed offshore installations. The simulation of past loading and structural degradation is then discussed. Guidance is provided on the selection of a suitable wave scatter diagram to represent past loading precisely. Guidelines are also provided on the selection of suitable corrosion wastage model parameters especially in cases where detailed degradation data is not available. The significance of the proposed guidelines is highlighted through a case study on an existing ageing jacket structure. Finally, conclusions are drawn and recommendations are made.
The Effect of Gap Space on Flow Induced Motions of Two Square Cylinders in Tandem
Authors: Wang Haibo , Zou Qunfeng , Zhang Li , Wu Chunmei , Ding Lin
Published: October 2017

When the Reynolds number is in the range of 30,000 and 100,000, the vibration characteristics of two square cylinders with elastic support and different tandem spacing are investigated by 2-D URANS simulations using OpenFOAM. In this work, the center to center distance (d) of two square cylinders is an important parameter and it increases from 2 to 6 diameters (D). Amplitude responses and frequency responses of first and second square cylinders are discussed and compared. The amplitude and frequency responses of first square cylinder are verified by the experiment results of Nemes et al. and they agree well in changing trends. The simulation results indicate that the amplitudes of the two square cylinders with different tandem spacing show an increasing trend with reduced velocity increasing. The maximum amplitudes reach 1.06D and 1.10D for the first and the second cylinders, respectively. And the oscillation of the second square cylinder is enhanced when d = 4D. The center to center distance has no significant effect on the frequency ratios of two square cylinders.