bluuebunny/crossref_metadata_2025_split huggingface dataset:
Probing the sRNA regulatory landscape of P. aeruginosa: post‐transcriptional control of determinants of pathogenicity and antibiotic susceptibility
Authors: Zhang Yi‐Fan , Han Kook , Chandler Courtney E. , Tjaden Brian , Ernst Robert K. , Lory Stephen 
Published: October 2017

SummaryDuring environmental adaptation bacteria use small regulatory RNAs (sRNAs) to repress or activate expression of a large fraction of their proteome. We extended the use of the in vivo RNA proximity ligation method toward probing global sRNA interactions with their targets in Pseudomonas aeruginosa and verified the method with a known regulon controlled by the PrrF1 sRNA. We also identified two sRNAs (Sr0161 and ErsA) that interact with the mRNA encoding the major porin OprD responsible for the uptake of carbapenem antibiotics. These two sRNAs base pair with the 5′ UTR of oprD leading to increase in resistance of the bacteria to meropenem. Additional proximity ligation experiments and enrichment for Sr0161 targets identified the mRNA for the regulator of type III secretion system. Interaction between the exsA mRNA and Sr0161 leads to a block in the synthesis of a component of the T3SS apparatus and an effector. Another sRNA, Sr006, positively regulates, without Hfq, the expression of PagL, an enzyme responsible for deacylation of lipid A, reducing its pro‐inflammatory property and resulting in polymyxin resistance. Therefore, an analysis of global sRNA‐mRNA interactions can lead to discoveries of novel pathways controlling gene expression that are likely integrated into larger regulatory networks.
Meta‐analysis on shift work and risks of specific obesity types
Authors: Sun M. , Feng W. , Wang F. , Li P. , Li Z. , Li M. , Tse G. , Vlaanderen J. , Vermeulen R. , Tse L. A. 
Published: October 2017

SummaryAimsThis systematic review and meta‐analysis evaluated the associations between shift work patterns and risks of specific types of obesity.MethodsPubMed was searched until March 2017 for observational studies that examined the relationships between shift work patterns and obesity. Odds ratio for obesity was extracted using a fixed‐effects or random‐effects model. Subgroup meta‐analyses were carried out for study design, specific obesity types and characteristics of shift work pattern.ResultsA total of 28 studies were included in this meta‐analysis. The overall odds ratio of night shift work was 1.23 (95% confidence interval = 1.17–1.29) for risk of obesity/overweight. Cross‐sectional studies showed a higher risk of 1.26 than those with the cohort design (risk ratio = 1.10). Shift workers had a higher frequency of developing abdominal obesity (odds ratio = 1.35) than other obesity types. Permanent night workers demonstrated a 29% higher risk than rotating shift workers (odds ratio 1.43 vs. 1.14).ConclusionThis meta‐analysis confirmed the risks of night shift work for the development of overweight and obesity with a potential gradient association suggested, especially for abdominal obesity. Modification of working schedules is recommended, particularly for prolonged permanent night work. More accurate and detailed measurements on shift work patterns should be conducted in future research.
Pollination and reproductive system of synchronopatric species of Cactaceae (Cactoideae) subject to interspecific flow of pollen: an example of ecological adaptation in the Brazilian Chaco
Authors: Ferreira B. H. S. , Gomes A. C. , Souza C. S. , Fabri J. R. , Sigrist M. R. 
Published: October 2017

Abstract

Three synchronopatric Cactaceae species, Echinopsis rhodotricha, Harrisia balansae and Praecereus saxicola, have mostly nocturnal anthesis and similar flowers, characteristics that motivated us to perform a comparative study of reproductive ecology.

Reproductive phenology was sampled monthly from December 2014 to November 2015. We describe floral biology, breeding system via pollination treatments and evaluate floral visitors from focal and filming observations. Pollen grains found on moth proboscis were compared among cactus species under light microscopy. We used fluorescent dye particles to test intra‐ and interspecific pollen flow.

These three species have extended flowering with greater intensity in the wet season, causing high overlap. They have white and hypocrateriformis flowers that open at twilight or nightfall and last about 15 h. H. balansae seems to be self‐incompatible, while E. rhodotricha presented self‐compatibility. P. saxicola presented self‐fertility, but most of the population seems to be self‐incompatible. We suggest sphingophily for the three species, but only P. saxicola was visited by Manduca rustica (Sphingidae). However, we observed pollen grains of all three species on the proboscis of moths, especially M. rustica and M. sexta. Prolonged anthesis allowed bees (herein considered as secondary pollinators) to visit flowers of E. rhodotricha and P. saxicola.

It can be concluded that the studied species share nocturnal and diurnal pollinators, suggesting interspecific pollen flow, which, however, could not be detected with fluorescent dye particles. In view of the low frequency of primary pollinators, it appears that these three species have different reproductive strategies, ensuring the fruiting and production of viable seeds.
Improved Sustainable Speed due to Thrusters With Ducted Propellers
Authors: Bulten Norbert , Stoltenkamp Petra 
Published: October 2017

The selection of the propulsion system is made in the concept design phase, based on a trial design point. Evaluation of the vessel design and the propulsion units has been based on model scale measurements for decades. Recent developments of CFD simulations have brought these numerical simulations to a sufficient mature level, to be considered as a good alternative for the model scale measurements. Comparisons of CFD results for model scale and full scale have revealed new interesting insights in the Reynolds scaling effects.
The actual operating conditions of offshore vessels are significantly different from the calm water trial condition. The optimized propulsion units for the trial condition are not per se the optimum solution for the actual operating conditions. A comparison has been made of two azimuth thruster types: pulling thruster with open propeller and a pushing thruster with ducted propeller. It has been shown that the performance in calm water is comparable for both type of thrusters. However, when the vessel is operating at increased loading, the benefits of the ducted propeller units become more pronounced. This is in the end reflected in an increased capability of keep a certain transit sailing speed in more harsh conditions.
Evaluation of CFD Analysis to Gather the Open-Water Characteristics of a Specific B-Series Propeller With Verification and Validation Assessments
Authors: Machado Lucas do Vale , Fernandes Antonio Carlos 
Published: October 2017

A very interesting topic in naval architecture is the choice of propeller. The engineer team should pay attention to several characteristics of the vessel to choose properly the most effective propeller for that specific application.
At the beginning of the Second World War, the diagrams of a well-known propeller design were published, the B-Series Propellers. They were tested at the Netherlands Ship Model Basin in Wageningen and analyzed with multiple polynomial regression analysis. Until today this propeller is studied because it possesses satisfactory efficiency and adequate cavitation properties. Besides that, open-water characteristics (KT, KQ and η0) are easy to get.
The purpose of this work is to evaluate the usefulness of CFD analysis to get the main characteristics of a propeller in order to make this selected process more effective, as long as with a lower cost is possible to analyze much more designs of propellers at a lower cost. A tool using Microsoft Excel was developed to draw any B-Series propeller. For this work was used a specific B-Series propeller, the B3.80. The CFD results are verified using Richardson Extrapolation and then validated against the propeller model results. The open-water characteristics are used for this purpose and the numerical results showed a fairly good agreement with the experimental data. Other interesting results of this propeller are shown too, e.g. the pressure distribution, streamlines and wall y+.
Long Term Analysis of TLP Extreme Tendon Tensions Using a Coupled Model and Comparison With the Contour Line Approach
Authors: Jimenez Puente Isabel , Lian Gunnar 
Published: October 2017

This paper presents a full long term analysis of a TLP extreme tendon tensions using the all seas approach, and its comparison to the results estimated by the contour line approach.
The analysis of the TLP tendon tension response is performed in the time domain using a coupled model where the floater is modelled in the software SIMO, while the tendon system is represented by a Finite Element Model in RIFLEX, including therefore the effects of non-linear restoring from the tendon system and bending and deformations of the tendons. The characteristic tendon tensions with q-annual probability of exceedance are estimated from a full long term analysis where both the short and long term variability are considered. These results are then compared to those obtained through the long term estimate from the contour line approach when assuming the 90th percentile for the worst sea state with q-annual probability of exceedance.
The results from the full long term analysis will allow us to verify the adequate percentile level to be used with a contour line approach when estimating extreme TLP tendon tensions.
Semi-Empirical Crest Distributions of Long-Crest Nonlinear Waves of Three-Hour Duration
Authors: Huang Zhenjia (Jerry) , Guo Qiuchen 
Published: October 2017

In wave basin model test of an offshore structure, waves that represent the given sea states have to be generated, qualified and accepted for the model test. For seakeeping and stationkeeping model tests, we normally accept waves in wave calibration tests if the significant wave height, spectral peak period and spectrum match the specified target values. However, for model tests where the responses depend highly on the local wave motions (wave elevation and kinematics) such as wave impact, green water impact on deck and air gap tests, additional qualification checks may be required. For instance, we may need to check wave crest probability distributions to avoid unrealistic wave crest in the test. To date, acceptance criteria of wave crest distribution calibration tests of large and steep waves of three-hour duration (full scale) have not been established.
The purpose of the work presented in the paper is to provide a semi-empirical nonlinear wave crest distribution of three-hour duration for practical use, i.e. as an acceptance criterion for wave calibration tests. The semi-empirical formulas proposed in this paper were developed through regression analysis of a large number of fully nonlinear wave crest distributions. Wave time series from potential flow simulations, computational fluid dynamics (CFD) simulations and model test results were used to establish the probability distribution. The wave simulations were performed for three-hour duration assuming that they were long-crested. The sea states are assumed to be represented by JONSWAP spectrum, where a wide range of significant wave height, peak period, spectral peak parameter, and water depth were considered. Coefficients of the proposed semi-empirical formulas, comparisons among crest distributions from wave calibration tests, numerical simulations and the semi-empirical formulas are presented in this paper.
Reducing Relative Horizontal Motion Between Cargo and HTV During Offshore Loading and Discharge
Authors: Peters Onno A. J. , Huijsmans René H. M. 
Published: October 2017

In Heavy Marine Transport it is common practice to dry-transport large and heavy floating offshore structures. In general, loading and discharge of these floating cargoes on- and from heavy transport vessels is done at sheltered locations like harbors where sea-state and swell conditions are insignificant. Often these locations are at large distance from operating fields of the offshore structures, which means that the structures need to be towed from- or to these fields. To save time and costs, it is beneficial to perform the loading and discharge operations in the field. This necessitates a reconsideration of the maximum allowable wave condition such as to perform the loading- and discharge operations within specified time frame whilst ensuring safety of crew, cargo and heavy transport vessel. Since precise positioning of the cargo on the HTV cribbing beams is of importance to support the cargo on its structural strong points, the allowed relative horizontal motion during loading or discharge operations is limited to a fraction of the width of these cribbing beams. When increasing the maximum allowable wave conditions, relative horizontal motions between heavy transport vessel and cargo easily exceed these limits if only the standard handling equipment is used. Also, the loads in the handling equipment may exceed safe limits.
This paper presents two methods including complementary equipment to reduce- and limit the relative horizontal motions. The first method is based on increasing the stiffness of the connection between cargo and heavy transport vessel. This means that there is a transition from a soft (standard handling) system with a low natural frequency to a stiff (clamping) system with high natural frequency. During this transition the system natural frequency will coincide with the wave frequent excitation force. Resonant behavior during the transition is avoided as the complementary equipment also employs a damping force. The second method is based on a closed-loop controller applied to the desired relative horizontal position. The resulting desired load to control the relative horizontal motion is then allocated to several line tension actuators. Contradictory to well-known Dynamic Positioning systems which control low frequent motions, motion control during offshore loading and discharge is performed on wave frequent behavior. This implies that the line tension actuators also need to deliver loads within a wave frequent time-frame. In fact, the peak tension needs to be obtained within a quarter of a wave period.
System design and simulation results are presented. Depending on the cargo type, different solutions and operational aspects are discussed. Simulations are done for a typical cargo where both methods to reduce the relative horizontal motions are utilized.
Concrete Modeling for Extreme Wave Slam Events
Authors: Wåsjø Kasper , Stavang Terje P. , Søreide Tore H. 
Published: October 2017

Experience from model tests has initiated a growing attention towards extreme wave slam as a critical load situation for offshore large volume structures. Most of the problem is related to the local slam pressure, which may go up to several MPa’s for 100-year and 10 000-year waves.
The paper deals with modeling techniques for marine concrete structures under extreme slam loading from waves where dynamic effects together with material softening play a major role for the response. Different analysis approaches for ultimate limit state (ULS) and accidental limit state (ALS) controls are discussed in view of reliability philosophy as basis for conventional design approach.
The present paper is devoted to the local impact scenario and the alternative approaches for response and capacity control involving non-linear time domain analyses. Conventional design schemes as based on linear elastic models for response calculation together with code specified capacity control often come out more conservative than non-linear approach. The paper demonstrates by case studies how softening of the structure in general reduces the response in terms of section forces.
A key issue when going from conventional linear approaches into non-linear techniques is to still keep an acceptable reliability level on the capacity control. Load and material factors are normally based on structures with limited non-linearity where linear response modeling is representative. Implementing non-linear material model in time domain analysis has a major challenge in limiting the sensitivity in response and capacity calculation. The paper demonstrates the way material model of concrete affects the section forces to go into local capacity control, and concludes on needed sensitivity analyses.
Practical approaches on the concrete slam problem together with resulting utilizations from the control are demonstrated. The full non-linear technique by response and capacity control in one analysis is also handled, using average material parameters and justifying safety factors for the effect of implementing characteristic lower strength of concrete in the capacity.
The paper ends up in a recommendation on non-linear time domain analysis procedure for typically slam problems. A discussion is also given on applicable design codes with attention to non-linear analysis.
Theoretical and Experimental Study of Heading Stability and Heading Control of a Turret-Moored FPSO
Authors: Kaasen Karl E. , Ludvigsen Halgeir , Nygaard Ivar , Aas Kristian 
Published: October 2017

The behaviour and characteristics of a turret-moored FPSO subjected to loading from waves, wind and current are investigated. Of particular importance is to find out if fishtailing instabilities may occur, and if such instability can be disclosed by simple criteria involving basic parameters of the system’s mathematical model. Eight cases from model tests are chosen for theoretical study and time domain simulation. Four of the cases involve heading control with thrusters.
For the stability study, a simplified linear model in sway and yaw is formulated. It is shown that the inherent characteristics of the model depend on the strengths and relative directions of the metocean processes. The eigenvalues of the sway-yaw model are computed for the eight selected cases to check the stability. A simple approximate criterion for heading stability is derived from the sway-yaw model. It is assumed, but not proven, that the criterion is a sufficiency criterion for stability.
Both the experiments and the simulations show that the eight cases are stable. This is also confirmed by the eigenvalues of the sway-yaw model, while the simple criterion wrongly deems several cases unstable. The simple stability criterion is therefore probably conservative, at least when there is significant damping in the system. In one additional hypothetical case with only wave excitation and weak or lacking stability, the simplified criterion agrees well with the model test and simulation.
Heading control is necessary when a heading different from the natural weathervaning heading is wanted. The controller used in the experiments and simulations is of simple SISO PID type. With control, the heading variations are reduced significantly.
Lateral Resistance of Pipes on Rocky Seabeds: Comparison Between Measurements and Models Based on Synthetic Seabeds
Authors: Griffiths Terry , White David , Draper Scott , Leighton Adam , Fogliani Antonino 
Published: October 2017

The behavior of pipelines, cables and umbilicals on rocky seabeds has to date received little research attention. This is despite the marine renewable energy and oil and gas industries relying on these ‘pipes’ to cross a variety of rocky seabed types in the presence of extreme metocean conditions. Present design solutions are challenging and costly, yet there remains a track record of in-service failures.
This paper forms part of a wider research effort being undertaken by the University of Western Australia (UWA) into pipe behavior on rocky seabeds. This work includes the effects intermittent gaps have on hydrodynamic forces, the effect of seabed roughness on enhanced boundary layer thickness and the validity of existing hydrodynamic force models for small diameter cables.
In this paper, the lateral resistance of pipes on rocky seabeds is investigated using both physical and numerical testing of model pipes over artificially-created rocky seabeds. Four model pipes of varying diameter have been displaced laterally over 1 m square model rocky seabeds, with a range of pipe to rock diameters. The lateral resistance of the physical pipe tests were recorded using load cells and a digital data-logger. Analysis of the physical test results has enabled comparison to (and refinement of) numerical models as well as improved understanding of the importance of different parameters. Our results show peak frictions above 6 arising under conditions where interface friction is only about 0.3, which contrasts dramatically with the friction value of 0.6 nominated in F109. This work contributes towards generation of new design methods suitable for application to field conditions.
Determining Thruster-Hull Interaction for a Drill-Ship Using CFD
Authors: Koop Arjen , Cozijn Hans , Schrijvers Patrick , Vaz Guilherme 
Published: October 2017

In this paper CFD results are presented for the thruster-hull interaction effects for a drillship with 6 azimuthing thrusters. The results using different approaches to model or simulate the propeller are compared and their advantages and disadvantages are discussed. The approaches investigated are the so-called Frozen Rotor approach, where the propeller rotation is modeled, the Actuator Disk approach with prescribed body forces and the unsteady Sliding Interface approach where the motion of the propeller is simulated in time.
First, open-water calculations for a tilted thruster are carried out using the Frozen Rotor approach. The open-water calculations are repeated using the Actuator Disk prescribing the propeller thrust and torque distribution obtained from the Frozen Rotor calculations. The results with Actuator Disk are very similar for the unit thrust and nozzle thrust compared to the results using the Frozen Rotor approach. Furthermore, the results using the Frozen Rotor or the Actuator Disk are very close to the experimental results for the nozzle thrust.
The thruster-hull interaction of one active thruster under the drillship is investigated using the Actuator Disk approach, the Frozen Rotor Approach and the Sliding Interface approach. A comparison to experimental results is presented for the thruster-hull interaction coefficients. Using the Actuator Disk a good agreement with the experiments is obtained. The results using the Actuator Disk and Sliding Interface are very similar to each other, but the computational costs for the Sliding Interface method are at least a factor 20 higher. The results using the Frozen Rotor deviate due to an unphysical wake behind the thruster.
Based on the results presented in this paper we conclude that, using the steady-state approach with the Actuator Disk, CFD can be a cost-efficient and accurate method to determine the thruster-hull interaction effects at bollard pull conditions for a typical offshore vessel.