bluuebunny/crossref_metadata_2025 huggingface dataset:
Brain processing of rectal sensation in adolescents with functional defecation disorders and healthy controls
Authors: Mugie S. M. , Koppen I. J. N. , van den Berg M. M. , Groot P. F. C. , Reneman L. , de Ruiter M. B. , Benninga M. A.
Published: October 2017

Background

Decreased sensation of urge to defecate is often reported by children with functional constipation (FC) and functional nonretentive fecal incontinence (FNRFI). The aim of this cross‐sectional study was to evaluate cerebral activity in response to rectal distension in adolescents with FC and FNRFI compared with healthy controls (HCs).

Methods

We included 15 adolescents with FC, 10 adolescents with FNRFI, and 15 young adult HCs. Rectal barostat was performed prior to functional magnetic resonance imaging (fMRI) to determine individual pressure thresholds for urge sensation. Subjects received 2 sessions of 5 × 30 seconds of barostat stimulation during the acquisition of blood oxygenation level‐dependent fMRI. Functional magnetic resonance imaging signal differences were analyzed using SPM8 in Matlab.

Key Results

Functional constipation and FNRFI patients had higher thresholds for urgency than HCs (P < .001). During rectal distension, FC patients showed activation in the anterior cingulate cortex, dorsolateral prefrontal cortex, inferior parietal lobule, and putamen. No activations were observed in controls and FNRFI patients. Functional nonretentive fecal incontinence patients showed deactivation in the hippocampus, parahippocampal gyrus, fusiform gyrus (FFG), lingual gyrus, posterior parietal cortex, and precentral gyrus. In HCs, deactivated areas were detected in the hippocampus, amygdala, FFG, insula, thalamus, precuneus, and primary somatosensory cortex. In contrast, no regions with significant deactivation were detected in FC patients.

Conclusions & Inferences

Children with FC differ from children with FNRFI and HCs with respect to patterns of cerebral activation and deactivation during rectal distension. Functional nonretentive fecal incontinence patients seem to resemble HCs when it comes to brain processing of rectal distension.
Global warming and obesity: a systematic review
Authors: An R. , Ji M. , Zhang S.
Published: October 2017

Global warming and the obesity epidemic are two unprecedented challenges mankind faces today. A literature search was conducted in the PubMed, Web of Science, EBSCO and Scopus for articles published until July 2017 that reported findings on the relationship between global warming and the obesity epidemic. Fifty studies were identified. Topic‐wise, articles were classified into four relationships – global warming and the obesity epidemic are correlated because of common drivers (n = 21); global warming influences the obesity epidemic (n = 13); the obesity epidemic influences global warming (n = 13); and global warming and the obesity epidemic influence each other (n = 3). We constructed a conceptual model linking global warming and the obesity epidemic – the fossil fuel economy, population growth and industrialization impact land use and urbanization, motorized transportation and agricultural productivity and consequently influences global warming by excess greenhouse gas emission and the obesity epidemic by nutrition transition and physical inactivity; global warming also directly impacts obesity by food supply/price shock and adaptive thermogenesis, and the obesity epidemic impacts global warming by the elevated energy consumption. Policies that endorse deployment of clean and sustainable energy sources, and urban designs that promote active lifestyles, are likely to alleviate the societal burden of global warming and obesity.
Interest of waiting time for spontaneous early reconnection after cavotricuspid isthmus ablation: A monocentric randomized trial
Authors: Marchandise Sébastien , Scavée Christophe , Barbraud Cynthia , de Meester de Ravenstein Christophe , Balola Bagalwa Mittérand , Goesaert Cédric , Reis‐Pinheiro Ivone , le Polain de Waroux Jean‐Benoit
Published: October 2017

Introduction

The aim of this study was to determine the rate of recurrent atrial flutter (AFl) after isolated cavotricuspid isthmus (CTI) ablation and to evaluate the impact of a waiting period with the search for early resumption of the CTI block on the long‐term outcome.

Method

Three hundred and nineteen consecutive patients referred for typical AFl ablation were randomly assigned to CTI ablation with continuous reevaluation of the CTI block during 30 minutes and early reablation if needed (waiting time [WT] + group, n  =  155) or to CTI ablation with no waiting period after proven bidirectional CTI block (WT − group, n  =  164). All patients were regularly followed‐up.

Result

In the WT+ group, 10 patients (6%) presented a recovery across the CTI (time to recovery: 17 ± 7′) and were reablated at the end of the waiting period. After a median follow‐up of 21 months, the rate of recurrent AFl was significantly higher in the WT − group as compared to the WT+ group (11.6% [19/164] vs 2.5% [4/155], respectively; P  =  0.007). However, no significant differences in the subsequent rate of AF were observed between the two groups (29% [WT −] vs 32% [WT+], P  =  0.66). During the follow‐up, 28 patients from the WT − group underwent a second ablation procedure (16 AFl redo and 12 AF ablation) versus 10 patients form the WT+ group (three AFl redo and seven AF ablation).

Conclusion

Waiting 30 minutes after CTI ablation to check for early resumption and early reablation allows for decreasing significantly the rate of recurrent atrial flutter.
The roles of alcohol dehydrogenase in patients with atrial fibrillation
Authors: Hu Yu‐Feng , Chang Yao‐Ting , Lin Yenn‐Jiang , Chang Shih‐Lin , Lo Li‐Wei , Huang Yen‐Hua , Liu Tze‐Tze , Chen Che‐Hong , Tuan Ta‐Chuan , Chao Tze‐Fan , Chung Fa‐Po , Liao Jo‐Nan , Te Abigail Louise D. , Huang Chi‐Ying F. , Chen Shih‐Ann
Published: October 2017

Background

Alcohol consumption is known to increase the risk of atrial fibrillation (AF). Whether the genotypes of alcohol‐metabolizing genes (alcohol dehydrogenase [ADH1B]) are associated with the risk of AF recurrence after catheter ablation remains unclear.

Methods and results

The ADH1B genotypes of 281 patients who received catheter ablation for AF were examined. We followed this group of patients to monitor their AF recurrence. Alcohol consumption levels of this cohort were evaluated before and after catheter ablation. There was no difference in the underlying diseases presented by the patients with different ADH1B genotypes. Regardless of the ADH1B genotypes, the amount of alcohol consumption was the only factor associated with left atrial dilatation. The ADH1B*2 alleles (hazard ratio: ADH1B*1/*2 vs *1/*1: 2.64; ADH1B*2/*2 vs *1/*1: 1.80, P = 0.02) and the levels of alcohol consumption were independently associated with AF recurrence in the patients with paroxysmal AF after catheter ablation. ADH1B polymorphisms were not associated with AF recurrence in the patients with nonparoxysmal AF. We also found that the association of increased AF recurrence with alcohol consumption and the ADH1B genotypes cannot be explained by mechanisms of systemic inflammation.

Conclusions

ADH1B*2/*2 genotype and amount of alcohol consumption increase the risk of AF recurrence after catheter ablation.
Reproductive traits and evolutionary divergence between Mediterranean crops and their wild relatives
Authors: Iriondo J. M. , Milla R. , Volis S. , Rubio de Casas R.
Published: October 2017

Changes in reproductive traits associated with domestication critically determine the evolutionary divergence between crops and their wild relatives, as well as the potential of crop plants to become feral. In this review, we examine the genetic mechanisms of plant domestication and the different types of selection involved, and describe the particularities of domestication of Mediterranean field crops with regard to their reproductive traits, showing illustrative examples. We also explore gene flow patterns between Mediterranean field crops and their wild relatives, along with their ecological, evolutionary and economic implications. Domestication entails multiple selective processes, including direct selection, environmental adaptation and developmental constraints. In contrast to clonal propagation in perennials, sexual reproduction and seed propagation in annuals and biennials have led to a distinct pathway of evolution of reproductive traits. Thus, the initial domestication and further breeding of Mediterranean field crops has brought about changes in reproductive traits, such as higher mean values and variance of seed and fruit sizes, reduced fruit and seed toxicity, non‐shattering seeds and loss of seed dormancy. Evolution under domestication is not a linear process, and bi‐directional gene flow between wild and crop taxa is a frequent phenomenon. Thus, hybridisation and introgression have played a very important role in determining the genetics of current cultivars. In turn, gene flow from crops to wild relatives can lead to introgression of crop genes into wild populations and potentially alter the characteristics of natural communities. In conclusion, plant evolution under domestication has not only changed the reproductive biology of cultivated taxa, its effects are multifaceted and have implications beyond agriculture.
Efficacy of UV‐C radiation to reduce seedborne anthracnose (Colletotrichum acutatum) from Andean lupin (Lupinus mutabilis)
Authors: Falconí C. E. , Yánez‐Mendizábal V.
Published: October 2017

The potential of UV‐C radiation of Andean lupin (Lupinus mutabilis) seeds to eradicate seedborne infections of anthracnose caused by Colletotrichum acutatum was investigated. UV‐C doses from 0 to 691.2 kJ m−2 (resulting from 0 to 96 h of exposure time) on disease incidence reduction and germination on artificially and naturally infected seed were evaluated. The degree of incidence reduction and seed germination was dependent on the dose of UV‐C. The UV‐C doses of 86.4 kJ m−2 and higher reduced incidence from 6% to 7% to undetectable levels, but these UV‐C doses also reduced seed germination. UV‐C can deleteriously affect physiological processes and overall growth. To assess its impact, L. mutabilis seeds irradiated with UV‐C doses of 57.6 and 86.4 kJ m−2 were grown. Seedlings grown from noninfected seed and UV‐C treated seed showed an increased concentration of chlorophyll and protein contents, as well as an increase in the activation of defence enzymes peroxidase and catalase, in comparison with plants grown from infected seed. UV‐C doses resulted in seed emergence and seedling dry weight rates that were similar to the noninfected control or better than the fungicide control. Moreover, 57.6 kJ m−2 reduced transmission of the pathogen from seed to the plantlets by 80%, while 86.4 kJ m−2 apparently eradicated the pathogen, under greenhouse conditions. The use of UV‐C, first reported here, is advantageous for controlling anthracnose in lupin.
Effects of the FITKids physical activity randomized controlled trial on conflict monitoring in youth
Authors: Drollette Eric S. , Pontifex Matthew B. , Raine Lauren B. , Scudder Mark R. , Moore R. Davis , Kao Shih‐Chun , Westfall Daniel R. , Wu Chien‐Ting , Kamijo Keita , Castelli Darla M. , Khan Naiman A. , Kramer Arthur F. , Hillman Charles H.
Published: October 2017

The present study investigated the effect of a 9‐month physical activity (PA) intervention on children's cardiorespiratory fitness levels and neuroelectric indices of conflict monitoring (i.e., error‐related negativity, ERN). Four hundred twenty‐eight preadolescent children (8–9 years old) were randomized into a PA intervention or wait‐list control group, and completed a fitness and cognitive control assessment (i.e., modified flanker task) at pre‐ and posttest. Following exclusion criterion, 308 children were included in the analyses (PA intervention: n = 139; wait‐list control: n = 169). Children in the intervention displayed greater improvements in fitness and response accuracy, which were accompanied by stability of ERN amplitude from pre‐ to posttest. In contrast, the control group revealed increased ERN amplitude at posttest compared to pretest, despite no change in fitness or task performance. These findings demonstrate the efficacy of daily PA for promoting children's fitness and underlying neural processes associated with effective conflict monitoring. Such findings have significant implications for promoting organized PA programs intended to foster overall physical and brain health in school age children.
Pain, fatigue and well‐being one to five years after lung transplantation – a nationwide cross‐sectional study
Authors: Forsberg Anna , Claëson Matilda , Dahlman Gull‐Britt , Lennerling Annette
Published: October 2017

Rationale and aim

Little is known about persistent pain after lung transplantation. Therefore, the aim was to present a multidimensional assessment of self‐reported pain 1‐5 years after lung transplantation and its relationship with fatigue and transplant‐specific well‐being.

Methods

This nationwide, cross‐sectional cohort study is part of the self‐management after thoracic transplantation study. A total of 117 lung recipients, all White, who were due for their annual follow‐up at one (n = 35), two (n = 28), three (n = 23), four (n = 20) and 5 years (n = 11) after lung transplantation were included. We used three instruments; the Pain‐O‐Meter (POM), which provides information about pain intensity, sensation, location and duration, the MFI‐19 fatigue instrument and the Organ Transplant Symptom and Well‐being Instrument (OTSWI). Permission to carry out this study was granted by the Regional Ethical Review Board in southern Sweden (D‐nr 2014‐124).

Results

The prevalence of pain was 51% after 1 year, 68% after 2 years, 69.5% after 3 years, 75% after 4 years and 54.5% after 5 years. Women experienced more pain than men. Lung recipients with pain reported lower well‐being and higher symptom distress but were not more fatigued than those without pain.

Study limitations

The limitations of this study are due to the cross‐sectional design. The recruitment of patients during the study period was probably affected by the different conditions regarding staffing at the outpatient lung transplant clinic in the two thoracic transplant centres in Sweden. The slightly different approach to the care of these patients in the pre, peri and postoperative setting contributes to the heterogeneity of the study population.

Conclusion

Chronic bodily pain up to 5 years after lung transplantation reduces perceived well‐being. Lung recipients with pain report higher symptom distress than those without pain.
Development of a nutrition knowledge questionnaire for young endurance athletes and their coaches
Authors: Heikkilä M. , Valve R. , Lehtovirta M. , Fogelholm M.
Published: October 2017

Both athletes and coaches should have adequate nutrition knowledge to understand the importance of diet on athletic performance, recovery, and health. Nutrition knowledge can be assessed reliably only by validated knowledge questionnaires. The aim of this study was to develop a reliable and valid questionnaire for assessing the nutrition knowledge of young endurance athletes and their coaches. The questionnaire was developed with an expert panel and pilot tested by athletes, coaches, and students. Content, face, and construct validities both as test‐retest reliability and internal consistency reliability were ensured when the current questionnaire was developed. Athletes (n = 16) and coaches (n = 13) pilot tested the 127‐item questionnaire. After item analysis and proposals from the expert panel, 41 items were removed. Internal consistency of the 86‐item questionnaire in the pilot study was 0.87, measured using Cronbach's α. Construct validity was evaluated by the difference in knowledge between nutrition (n = 20) and humanities students (n = 22). Nutrition students had significantly higher knowledge scores (P < .001). Test‐retest reliability for all knowledge sections between those groups was 0.85 measured using Pearson's r. Final adjustments to the questionnaire were made on the grounds of feedback from the respondents and proposals from the experts (n = 6). These adjustments resulted in minor changes in the construct of the items, the layout of the questionnaire, and the removal of 7 items. The final questionnaire had 79 items. The questionnaire can be used to measure the overall nutrition knowledge of endurance athletes and their coaches and to find potential gaps in nutrition knowledge.
Safe and sustainable plasmapheresis
Authors: Pink J. , Bell B. , Kotsiou G. , Wright S. , Thyer J.
Published: October 2017

Background and Objectives

Our aim is to present the recent Australian experience in trying to optimise collections from our apheresis program to meet the challenge of increasing demand for intravenous immunoglobulin. This is against a background of decreasing red cell demand, resulting in less recovered plasma from whole blood.

Materials and Methods

We extracted data from our donor and product databases and from targeted internal studies and audits. Data was analysed to determine the effects of donor factors, changes in collection processes and other interventions on the plasma volume, plasma quality, donor safety and donor return rates.

Results

Vasovagal reactions remain a key adverse reaction in apheresis with implications not only for donor safety but also for donor return and therefore supply. Many factors influence reaction rates including donor selection and the details of the apheresis procedure. Other apheresis related complications include citrate reactions, iron deficiency and potentially bone health in long‐term donors. Changes in collection procedures can also affect product quality, which may negate benefits of increasing volume. Another key to maintaining supply is to optimise the frequency of donor visits, a major challenge in the non‐remunerated donor setting.

Conclusion

In a time of increasing demand it is important to optimise immunoglobulin yield by retaining donors, increasing visit frequency and maximising volumes from each visit, whilst carefully balancing the risk of adverse reactions. Interventions must be assessed in terms of donor safety and also product yield. Both must be optimised if sustainability of plasma supply is to be achieved.
Rapid decline in MyHC I(β) mRNA expression in rat soleus during hindlimb unloading is associated with AMPK dephosphorylation
Authors: Vilchinskaya Natalia A. , Mochalova Ekaterina P. , Nemirovskaya Tatiana L. , Mirzoev Timur M. , Turtikova Olga V. , Shenkman Boris S.
Published: October 2017

Key points

Inactivation of a skeletal muscle results in slow to fast myosin heavy chain (MyHC) shift.

AMP‐activated protein kinase (AMPK) can be implicated in the regulation of genes encoding the slow MyHC isoform.

Here we report that AMPK dephosphorylation after 24 h of mechanical unloading can contribute to histone deacetylase (HDAC) nuclear translocation; activation of AMPK prevents HDAC4 nuclear accumulation after 24 h of unloading and AMPK dephosphorylation inhibits slow MyHC expression following 24 h of unloading.

Our data indicate that AMPK dephosphorylation during the first 24 h of mechanical unloading has a significant impact on the expression of MyHC isoforms in rat soleus causing a decrease in MyHC I(β) pre‐mRNA and mRNA expression as well as MyHC IIa mRNA expression.

One of the key events that occurs during skeletal muscle inactivation is a change in myosin phenotype, i.e. increased expression of fast isoforms and decreased expression of the slow isoform of myosin heavy chain (MyHC). It is known that calcineurin/nuclear factor of activated T‐cells and AMP‐activated protein kinase (AMPK) can regulate the expression of genes encoding MyHC slow isoform. Earlier, we found a significant decrease in phosphorylated AMPK in rat soleus after 24 h of hindlimb unloading (HU). We hypothesized that a decrease in AMPK phosphorylation and subsequent histone deacetylase (HDAC) nuclear translocation can be one of the triggering events leading to a reduced expression of slow MyHC. To test this hypothesis, Wistar rats were treated with AMPK activator (AICAR) for 6 days before HU as well as during 24 h of HU. We discovered that AICAR treatment prevented a decrease in pre‐mRNA and mRNA expression of MyHC I as well as MyHC IIa mRNA expression. Twenty‐four hours of hindlimb suspension resulted in HDAC4 accumulation in the nuclei of rat soleus but AICAR pretreatment prevented this accumulation. The results of the study indicate that AMPK dephosphorylation after 24 h of HU had a significant impact on the MyHC I and MyHC IIa mRNA expression in rat soleus. AMPK dephosphorylation also contributed to HDAC4 translocation to the nuclei of soleus muscle fibres, suggesting an important role of HDAC4 as an epigenetic regulator in the process of myosin phenotype transformation.
Reproduction Differentially Affects Trabecular Bone Depending on Its Mechanical Versus Metabolic Role
Authors: de Bakker Chantal M. J. , Tseng Wei-Ju , Li Yihan , Zhao Hongbo , Altman-Singles Allison R. , Jeong Yonghoon , Robberts Juhanna , Han Lin , Kim Do-Gyoon , Sherry Liu X.
Published: October 2017

During pregnancy and lactation, the maternal skeleton provides calcium for fetal/infant growth, resulting in substantial bone loss, which partially recovers after weaning. However, the amount of bone that is lost and the extent of post-weaning recovery are highly variable among different skeletal sites, and, despite persistent alterations in bone structure at some locations, reproductive history does not increase postmenopausal fracture risk. To explain this phenomenon, we hypothesized that the degree of reproductive bone loss/recovery at trabecular sites may vary depending on the extent to which the trabecular compartment is involved in the bone’s load-bearing function. Using a rat model, we quantified the proportion of the load carried by the trabeculae, as well as the extent of reproductive bone loss and recovery, at two distinct skeletal sites: the tibia and lumbar vertebra. Both sites underwent significant bone loss during pregnancy and lactation, which was partially recovered post-weaning. However, the extent of the deterioration and the resumption of trabecular load-bearing capacity after weaning varied substantially. Tibial trabecular bone, which bore a low proportion of the total applied load, underwent dramatic and irreversible microstructural deterioration during reproduction. Meanwhile, vertebral trabecular bone bore a greater fraction of the load, underwent minimal deterioration in microarchitecture, and resumed its full load-bearing capacity after weaning. Because pregnancy and lactation are physiological processes, the distinctive responses to these natural events among different skeletal sites may help to elucidate the extent of the trabecular bone’s structural versus metabolic functions.
Strain
Distribution of Intact Rat Rotator Cuff Tendon-to-Bone Attachments and Attachments With
Defects
Authors: Locke Ryan
C. , Peloquin John
    M. , Lemmon Elisabeth
A. , Szostek Adrianna , Elliott Dawn
M. , Killian Megan
L.
Published: October 2017

This study aimed to experimentally track the tissue-scale strains of the tendon–bone attachment with and without a localized defect. We hypothesized that attachments with a localized defect would develop strain concentrations and would be weaker than intact attachments. Uniaxial tensile tests and digital image correlation were performed on rat infraspinatus tendon-to-bone attachments with defects (defect group) and without defects (intact group). Biomechanical properties were calculated, and tissue-scale strain distributions were quantified for superior and inferior fibrous and calcified regions. At the macroscale, the defect group exhibited reduced stiffness (31.3±3.7 N/mm), reduced ultimate load (24.7±3.8 N), and reduced area under the curve at ultimate stress (3.7±1.5 J/m2) compared to intact attachments (42.4±4.3 N/mm, 39.3±3.7 N, and 5.6±1.4 J/m2, respectively). Transverse strain increased with increasing axial load in the fibrous region of the defect group but did not change for the intact group. Shear strain of the superior fibrous region was significantly higher in the defect group compared to intact group near yield load. This work experimentally identified that attachments may resist failure by distributing strain across the interface and that strain concentrations develop near attachment defects. By establishing the tissue-scale deformation patterns of the attachment, we gained insight into the micromechanical behavior of this interfacial tissue and bolstered our understanding of the deformation mechanisms associated with its ability to resist failure.
Predicting Behavior of Sucker-Rod Pumping Systems With Optimal Control
Authors: Chen Zengshi , White Luther W. , Zhang Huimin
Published: October 2017

An approach of optimal control is developed for predicting the behavior of sucker-rod pumping systems. Our method provides the error correction in prediction, and accurately generates polished rod and intermediate-depth work dynagraphs under any bottom-hole pump condition of vertical oil wells. From the prediction perspective, any normal or abnormal pumping condition of vertical oil wells can be simulated by our method. Our method can replace the conventional prediction methods and are definitely able to predict the complex pumping conditions which the conventional prediction methods cannot predict due to their technical constraints. The prediction results from our method will be of great values to improve the design, selection, installation, and operation of sucker-rod pumping systems. From the diagnostic point of view, a complete databank of surface work dynagraphs corresponding to all the downhole pump conditions of vertical oil wells can be generated by our method and can be used as an expert knowledge system for diagnostic of the sucker-rod pumping systems in the operation situations that only the surface work dynagraphs but not the pump dynagraphs are available. Our method is also a good tool to conveniently generate surface work dynagraphs for pump diagnostic emulators.
Impact of Air Quality and Site Selection on Gas Turbine Engine Performance
Authors: MacPhee David W. , Beyene Asfaw
Published: October 2017

Air pollution can have detrimental effects on gas turbine performance leading to blade fouling, which reduces power output and requires frequent cleanings. This issue is a fairly well-known phenomenon in the power industry. However, site selection for gas turbine installation on the basis of air quality is rarely part of the decision-making process, mainly due to lack of geographical options especially in an urban environment or perhaps due to a simple assumption that air quality at a local micro-level has no impact on the performance of the engine. In this paper, we perform a computational fluid dynamics (CFD) study on an area surrounding a combined heat and power (CHP) facility to assess the impact of local wind distribution on air quality and the performance of a gas turbine engine. Several aerodynamic properties are suggested as possible indicators of air quality and/or high airborne particulate concentration. These indicators are then compared to data collected at various points in and around the site. The results suggest that through post-processing of a simplified CFD simulation analyzing the adjacent terrain, a continuous map of field variables can be obtained and help designers locate future CHP or gas turbine power plants in regions of lower particulate concentrations. This, in turn, would greatly increase efficiency and cost-effectiveness of the proposed power plant.
Experimental Study on Flow Around an Array of Four Cylinders With Different Section Geometries
Authors: Gonçalves Rodolfo T. , Hirabayashi Shinichiro , Suzuki Hideyuki
Published: October 2017

Experiments were carried out in a towing tank regarding the flow around a stationary array of four cylinders with low aspect ratio, H/L = 1.5, piercing the water free surface. One isolated cylinder and one array of 4 cylinders were tested; this number of cylinders corresponds to the number of columns of a typical multi-column offshore floater system, such as semi-submersibles and TLP platforms. Three different geometries of cylinder sections were studied: circular, square and diamond. The aims are to better understand the influence of the relative position of the cylinders on the flow around this type of structure; to create a reliable database for CFD studies and afterward to use this research in VIM calculations for free multi-columns systems. Two parameters were investigated for a distance between column centers S/L = 3: current incidence angles 0, 22.5 and 45 degrees and column section geometries. The Reynolds number range covers from 50,000 up to 250,000. Forces were measured in each column by using a three degree-of-freedom load cell. Results of lift and drag forces are presented for each column separately and for the whole system. This paper is a piece of an extensive experimental study on flow around an array of multi-cylinders.
On the Influence of Environmental Contour Method in Estimating Extreme Structural Response
Authors: Vanem Erik
Published: October 2017

Environmental contours are often applied in probabilistic structural reliability analysis in order to identify extreme environmental conditions that may give rise to extreme loads and responses. The perhaps most common way of establishing such environmental contours are based on the Rosenblatt transform and the IFORM approximation (Inverse First Order Reliability Method), but recently an alternative approach based on direct Monte Carlo simulations with importance sampling has been proposed. A recent comparison study revealed that there might be rather large differences in certain parts of the contours and for certain joint environmental models. In particular, the alternative contour method yields convex contours by design, whereas the traditional contours may be convex or non-convex.

In this paper, comparison studies that include applications on a few structural examples are presented. Comparing the contours with known response surfaces, one may investigate how large the differences between the contour methods may be, and compare this to the correct extreme response estimated by simulation studies. These case studies clearly illustrate the influence of the environmental contour calculation method on the estimated extreme response. Whereas the different methods yield comparable results for some structural problems, they may give very different estimates of the extreme response for other. It is demonstrated that in certain cases, the estimates from some of the contour methods are highly conservative, whereas they in other cases might be very optimistic. The reason for these results are discussed and some requirements on the response functions for obtaining conservative estimates will be stated.
A Study on Forced Vibration of Double Bottom Structure due to Whipping on an Ultra Large Container Ship
Authors: Kawasaki Yohei , Okada Tetsuo , Kobayakawa Hiroaki , Amaya Ichiro , Miyashita Tetsuji , Nagashima Tomoki , Neki Isao
Published: October 2017

Worldwide expansion of economy has brought about prominent and rapid enlargement of container ships. Their greater beam has caused more flexible double bottom structure, giving rise to concerns about its adverse effect to the ultimate strength of hull girder. To accurately assess the ultimate strength of hull girder, it is essential to precisely grasp how the double bottom structures behave in the actual sea state, in terms of whipping and vibratory response as well as wave frequency response.

In this paper, the authors investigated structural behavior of the double bottom of a 14,000 TEU ultra large container ship in long-crested irregular head seas. Firstly, time domain ship motion and wave pressure on the hull surface was obtained through numerical analysis using Rankine source method. Subsequently, the obtained loads were applied to 3-dimensional whole ship finite element model, and time domain elastic responses of all over the hull structures were analyzed using Newmark-β method in terms of both whipping and wave frequency responses.

As a result, regarding the wave frequency response, it was found that maximum wave induced upward bending of the midship double bottom structures is exerted almost simultaneously with the maximum wave induced hogging hull girder bending moment. The correlation factors between the double bottom bending and the hull girder bending were about 0.94 around the midship region, and they decreased in the fore and aft region.

Regarding the whipping and vibratory response, it was found that large whipping response induces forced vibration of the double bottom structures, especially in the midship region. Because of the higher natural frequencies of the double bottom structures compared with that of whipping, the double bottom structures are excited in the same phase as the hull girder whipping, resulting in superimposed longitudinal stresses in way of the bottom shell plating.

From these observations, it can be concluded that the local bending behavior of the double bottom structures adversely affects the hull girder ultimate strength, both in terms of wave loads and whipping loads, and it is necessary to take sufficient care to the double bottom rigidity.
Inertial Sensors for Risk-Based Redundancy in Dynamic Positioning
Authors: Bryne Torleiv H. , Rogne Robert H. , Fossen Thor I. , Johansen Tor A.
Published: October 2017

In this paper we present an alternative configuration of sensors, position and heading reference systems for dynamically positioned (DP) vessels. The approach uses a sensor structure based on low-cost inertial measurements units (IMUs), satisfying fault tolerance against single-point failures that is at the essence of the IMO guidelines for both DP class 2 and 3 vessels. Recent results have shown that dual-redundant position and heading reference systems are sufficient to prevent loss of position within some well-defined time horizons by exploiting sensor fusion of the reference systems and triple-redundant MEMS-based IMUs. These IMUs also function as Vertical Reference Units (VRUs), since vessel motions is obtained using the same IMU configuration and sensor fusion framework. In this proposition, the acceleration measurements provided by the IMUs make wind and other force sensors unnecessary, except possibly for an advisory role. The proposed framework has the potential to significantly reduce the cost of dynamic positioning systems without compromising safety.
Multi-Objective Optimization of Subsea Pipeline Routes in Shallow Waters
Authors: Baioco Juliana Souza , Albrecht Carl Horst , Lima Beatriz Souza Leite Pires de , Jacob Breno Pinheiro , Rocha Djalene Maria
Published: October 2017

This paper presents recent advances regarding a computational tool, based in Evolutionary Algorithms, for the synthesis and optimization of submarine pipeline routes. Previous works by the authors have focused on some specific issues related to the development of this tool, including the incorporation of engineering criteria such as on-bottom stability (OBS), VIV-induced fatigue in free-spanning pipelines, and flow assurance. Now, this work studies the influence of different OBS criteria for particular scenarios in shallow waters, where it is expected that the environmental loads of wave and current play a more important role on the hydrodynamic stability of the pipe. Case studies are presented, to compare the influence of OBS criteria proposed by the DNV RP-F109 code (Absolute Lateral Static Stability, and Generalized Lateral Stability), both implemented into a multi-objective procedure (using specialized algorithms based on the Pareto approach) along with other engineering criteria (VIV-induced fatigue and multiphase flow).
T-N Curves and Fracture Mechanics Based Mooring Fatigue Analysis for a Semi-Submersible
Authors: Xue Xutian , Chen Nian-Zhong
Published: October 2017

This paper is to perform T-N curves and fracture mechanics based fatigue analysis for mooring lines of a semi-submersible installed in Gulf of Mexico (GoM). The wave frequency (WF) and the low frequency (LF) load processes are regarded as two random processes and the load combination of the two processes is considered. Frequency-domain analysis is then conducted for calculating the tension ranges along hybrid-material mooring lines induced by motions of WF, LF and the combined WF and LF. The narrow-banded spectral method is used for calculating the mooring line tension and the fatigue damage of mooring lines is estimated by T-N curves and fracture mechanics based approaches. The fracture mechanics based analysis is combined with a finite element analysis to predict crack propagation at different locations of a studless chain link. It was found that the crown section of a mooring chain is the most critical location subjected to fatigue failure in a studless chain link. The most critical points prone to fatigue failure of the catenary and taut mooring systems designed for the semi-submersible are at the bottom end of top line and the top end of bottom line, respectively. Also, fatigue lives of mooring lines in the catenary mooring system are generally longer than those of the taut mooring system. In addition, a comparison between fatigue lives of mooring lines predicted by T-N curves and fracture mechanics based approaches shows that the results estimated by both approaches are generally comparable.
Investigation on Standing and Traveling Wave Response Patterns in Long Flexible Risers
Authors: Joshi V. , Gurugubelli P. S. , Yenduri A. , Jaiman R. K. , Adaikalaraj P. F. B.
Published: October 2017

Due to the complexity involved in the vortex-induced vibration (VIV) of long offshore risers, the fundamental understanding of the coupled kinematics and dynamics of the standing and traveling waves is not well established. In the present contribution, a systematic numerical study on slender flexible riser immersed in a turbulent flow is performed on a flexible riser pinned at both the ends to investigate the standing and traveling wave responses. This wake-body resonance problem requires a stable coupling of the Navier-Stokes equation with the low mass flexible riser structure subjected to strong inertial effects from the surrounding fluid flow. A partitioned iterative scheme that relies on the nonlinear interface force corrections is employed for the modeling of coupled fluid-riser problem. The study here includes a flexible cylindrical riser considered as a long tensioned beam via linear modal analysis. Full three-dimensional simulations are performed on the flexible riser exposed to two different inflow conditions: uniform and linearly sheared. At first, the response characteristics of the riser model are validated with experimental measurements under pinned-pinned condition for uniform current. A detailed analysis is performed on the response characteristics and vorticity dynamics at various locations along the span of the flexible riser. Our simulations show that for uniform inflow condition, the flexible riser exhibits a standing wave-like phenomenon. On the other hand, for linearly sheared inflow, a traveling wave response is observed for both cross-flow and inline oscillations. These traveling waves travel from the top point to the bottom point.
Computation of Wave Impact Pressures and Kinematics During Plunging Breaking Wave Interaction With a Vertical Cylinder Using CFD Modelling
Authors: Alagan Chella Mayilvahanan , Bihs Hans , Myrhaug Dag , Arntsen Øivind Asgeir
Published: October 2017

Wave loads from breaking waves on offshore wind turbine (OWT) substructures in shallow waters still remain uncertain. The interaction of breaking waves with structures is characterized by complex free surface deformations, instantaneous impact of the water mass against the structure and consequently large wave forces on the structures. The main objective of the paper is to investigate wave impact pressures and kinematics during the interaction of breaking waves with a vertical cylinder using the open-source CFD model REEF3D. The model is based on the Reynolds-Averaged Navier-Stokes (RANS) equations coupled with the level set method (LSM) and k-ω turbulence model. Three wave impact conditions are considered in the present study. The numerically simulated free surface deformations around the cylinder during the breaking wave interaction are also presented for different wave impact conditions. For three wave impact conditions, the wave impact pressure and the horizontal and vertical components of the particle velocity are computed in front of the cylinder and analyzed. The pressure and velocity profile at their maximum values are also examined and discussed. In addition, the total force is calculated for three breaking conditions and they are correlated with the pressure and kinematics during the interaction.
Numerical Investigation on Vessel Motion-Induced VIV for a Free Hanging Riser Under Small Keulegan-Carpenter Numbers
Authors: Wang Jungao , Joseph Rohan Shabu , Ong Muk Chen , Jakobsen Jasna Bogunović
Published: October 2017

A free-hanging riser is a typical riser configuration seen in the disconnected drilling riser, the water-intake riser and the deep-sea mining riser. In offshore productions, these marine risers will move back and forth in water and further generate an equivalent oscillatory current around themselves, due to the vessel motions. Both in marine operations in the field and model tests, it has been reported that such oscillatory current lead to riser vortex-induced vibration (VIV) and cause structural fatigue damage. Recently, there have been some attempts to numerically predict vessel motion-induced VIV on the compliant production risers, with emphasize on relatively large Keulegan-Carpenter (KC) numbers. In the real marine operations, the risers experience small KC number scenarios during most of their service life. Therefore, the investigation of vessel motion-induced VIV under small KC number is of great significance, especially considering its contribution to fatigue damage. In this paper, numerical investigation of VIV of a free-hanging riser attached to a floating vessel is carried out. A new response frequency model for vessel motion-induced VIV under small KC numbers is proposed and implemented in VIVANA. Validation of the proposed numerical methodology is performed against the published experimental results, where a good agreement is achieved.
Improved In-Line VIV Prediction for Combined In-Line and Cross-Flow VIV Responses
Authors: Yin Decao , Passano Elizabeth , Larsen Carl M.
Published: October 2017

Slender marine structures are subjected to ocean currents, which can cause vortex-induced vibrations (VIV). Accumulated damage due to VIV can shorten the fatigue life of marine structures, so it needs to be considered in the design and operation phase.

VIV prediction tools are based on hydrodynamic coefficients, which are obtained from forced motion experiments on a circular cylinder. Most of the forced motion experiments apply harmonic motions in either in-line (IL) or cross-flow (CF) direction. Combined IL and CF forced motion experiments are also reported. However, measured motions from flexible pipe VIV tests contain higher order harmonic components, which have not yet been extensively studied.

This paper presents results from conventional forced motion VIV experiments, but using measured motions taken from a flexible pipe undergoing VIV. The IL excitation coefficients were used by semi-empirical VIV prediction software VIVANA to perform combined IL and CF VIV calculation. The key IL results are compared with NDP flexible pipe model test results. By using present IL excitation coefficients, the prediction of IL responses for combined IL and CF VIV responses is improved.
Tension-Tension Testing of a Novel Mooring Rope Construction
Authors: Weller S. D. , Halswell P. , Johanning L. , Kosaka T. , Nakatsuka H. , Yamamoto I.
Published: October 2017

Synthetic fibre ropes are in widespread use in maritime applications ranging from lifting to temporary and permanent mooring systems for vessels, offshore equipment and platforms. The selection of synthetic ropes over conventional steel components is motivated by several key advantages including selectable axial stiffness, energy absorption (and hence load mitigation), fatigue resistance and low unit cost. The long-term use of ropes as safety critical components in potentially high dynamic loading environments necessitates that new designs are verified using stringent qualification procedures. The International Organization for Standardization (ISO) is one certification body that has produced several guidelines for the testing of synthetic ropes encompassing quasi-static and dynamic loading as well as fatigue cycling.

This paper presents the results of tension-tension tests carried out to ISO 2307:2010, ISO 18692:2007(E) and ISO/TS 19336:2015(E) on three different 12-strand rope constructions manufactured by Ashimori Industry Co. Ltd from polyester and Vectran® fibres. The purpose of the tests was to characterise the performance of a novel 12-strand construction and compare this to a conventional 12-strand construction. Utilising the Dynamic Marine Component test facility (DMaC) at the University of Exeter several key performance metrics were determined including; elongation, minimum break load (MBL) and quasi-static and dynamic stiffness. During the ISO 2307:2010(E) test programme the samples were tested dry and during the ISO 18692:2007(E) and ISO/TS 19336:2015(E) test programmes the samples were fully submerged in tap water after being soaked for at least 24 hours. Two methods were used to quantify sample extension: i) an optical tracking system and ii) a draw-wire potentiometer. Axial compression fatigue and cyclic loading endurance tests were also carried out on two Vectran® samples. Further load-to-failure tests and sample analysis were also carried out by Ashimori Industry Co. Ltd.

It was found that the MBL of the samples exceeded the values specified by the manufacturer (by 7.7–29.5% for the polyester samples) with failure occurring at the splices in all cases and minor abrasion noted in several locations. The measured MBL of the novel polyester Straight Strand Rope (SSR) construction was up to 16% higher than the conventional construction with increases of quasi-static and dynamic stiffness of up to 6.8%. Differences between the viscoelastic and viscoplastic behaviour of the samples were also noted. The data obtained during these tests will provide insight into the behaviour of these materials and different rope constructions which will be of use to rope manufacturers, mooring system designers in addition to offshore equipment and vessel operators.