bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phosphatase activity of the voltage‐sensing phosphatase, VSP, shows graded dependence on the extent of activation of the voltage sensor
Authors: Sakata Souhei , Okamura Yasushi 
Published: November 2013

Key points
The voltage‐sensing phosphatase (VSP) consists of the voltage sensor and the phosphatase domain. The voltage sensor movement is coupled to the phosphatase activity.
To uncover the coupling mechanisms between the two domains, we made a voltage sensor mutant of VSP. Our analyses showed that this voltage sensor moves in two steps.
Measurements revealed that the phosphatase activity of this mutant is associated with both the first and second step of the voltage sensor movements.
Results suggest that the phosphatase activity of VSP shows graded dependence on the extent of activation of the voltage sensor.
AbstractThe voltage‐sensing phosphatase (VSP) consists of a voltage sensor and a cytoplasmic phosphatase region, and the movement of the voltage sensor is coupled to the phosphatase activity. However, its coupling mechanisms still remain unclear. One possible scenario is that the phosphatase is activated only when the voltage sensor is in a fully activated state. Alternatively, the enzymatic activity of single VSP proteins could be graded in distinct activated states of the voltage sensor, and partial activation of the voltage sensor could lead to partial activation of the phosphatase. To distinguish between these two possibilities, we studied a voltage sensor mutant of zebrafish VSP, where the voltage sensor moves in two steps as evidenced by analyses of charge movements of the voltage sensor and voltage clamp fluorometry. Measurements of the phosphatase activity toward phosphatidylinositol 4,5‐bisphosphate revealed that both steps of voltage sensor activation are coupled to the tuning of phosphatase activities, consistent with the idea that the phosphatase activity is graded by the magnitude of the movement of the voltage sensor.
Transition between fast and slow gamma modes in rat hippocampus area CA1 in vitro is modulated by slow CA3 gamma oscillations
Authors: Pietersen Alexander N. J. , Ward Peter D. , Hagger‐Vaughan Nicholas , Wiggins James , Jefferys John G. R. , Vreugdenhil Martin 
Published: November 2013

Key points
The synchronisation of neuronal activity at gamma frequencies (30–100 Hz) could determine the effectiveness of neuronal communication.
Gamma oscillations in the CA1 region of the hippocampus in vitro was thought to be dependent on gamma oscillations generated in area CA3, but in vivo CA1 can generate gamma oscillations independently.
In this study we found that activating acetylcholine receptors induced stable gamma oscillations in the CA1 local network isolated in slices in vitro that were faster than those in CA3, but relied on similar neuronal circuitry involving feedback inhibition.
Gamma frequency inputs from CA3 (spontaneous in intact hippocampal slices or stimulated in isolated CA1) can suppress the local fast gamma oscillation in CA1 and force it to adopt the slower CA3 oscillation through feed‐forward inhibition.
This modulation could allow CA1 to alternate between effective communication with the entorhinal cortex and CA3, which may regulate memory encoding and memory recall phases.
AbstractHippocampal gamma oscillations have been associated with cognitive functions including navigation and memory encoding/retrieval. Gamma oscillations in area CA1 are thought to depend on the oscillatory drive from CA3 (slow gamma) or the entorhinal cortex (fast gamma). Here we show that the local CA1 network can generate its own fast gamma that can be suppressed by slow gamma‐paced inputs from CA3. Moderate acetylcholine receptor activation induces fast (45 ± 1 Hz) gamma in rat CA1 minislices and slow (33 ± 1 Hz) gamma in CA3 minislices in vitro. Using pharmacological tools, current‐source density analysis and intracellular recordings from pyramidal cells and fast‐spiking stratum pyramidale interneurons, we demonstrate that fast gamma in CA1 is of the pyramidal–interneuron network gamma (PING) type, with the firing of principal cells paced by recurrent perisomal IPSCs. The oscillation frequency was only weakly dependent on IPSC amplitude, and decreased to that of CA3 slow gamma by reducing IPSC decay rate or reducing interneuron activation through tonic inhibition of interneurons. Fast gamma in CA1 was replaced by slow CA3‐driven gamma in unlesioned slices, which could be mimicked in CA1 minislices by sub‐threshold 35 Hz Schaffer collateral stimulation that activated fast‐spiking interneurons but hyperpolarised pyramidal cells, suggesting that slow gamma frequency CA3 outputs can suppress the CA1 fast gamma‐generating network by feed‐forward inhibition and replaces it with a slower gamma oscillation driven by feed‐forward inhibition. The transition between the two gamma oscillation modes in CA1 might allow it to alternate between effective communication with the medial entorhinal cortex and CA3, which have different roles in encoding and recall of memory.
GPGPU Accelerated 3-Axis CNC Machining Simulation
Authors: Konobrytskyi Dmytro , Kurfess Thomas , Tarbutton Joshua , Tucker Tommy 
Published: November 2013

GPUs (Graphics Processing Units), traditionally used for 3D graphics calculations, have recently got an ability to perform general purpose calculations with a GPGPU (General Purpose GPU) technology. Moreover, GPUs can be much faster than CPUs (Central Processing Units) by performing hundreds or even thousands commands concurrently. This parallel processing allows the GPU achieving the extremely high performance but also requires using only highly parallel algorithms which can provide enough commands on each clock cycle.
This work formulates a methodology for selection of a right geometry representation and a data structure suitable for parallel processing on GPU. Then the methodology is used for designing the 3-axis CNC milling simulation algorithm accelerated with the GPGPU technology. The developed algorithm is validated by performing an experimental machining simulation and evaluation of the performance results.
The experimental simulation shows an importance of an optimization process and usage of algorithms that provide enough work to GPU. The used test configuration also demonstrates almost an order of magnitude difference between CPU and GPU performance results.
Uncertainty in Peakedness Factor Estimation by JONSWAP Spectral Fitting From Measurements
Authors: Saulnier Jean-Baptiste 
Published: November 2013

In offshore engineering, JONSWAP shapes are commonly used to fit wave spectra and characterise the peakedness of the sea state. The latter is defined as γ, the so-called peak enhancement factor, which is as large as the peak is acute, with values generally ranging from ∼1 to 7 (1 and 3.3 being usually adopted for fully-developed and average wind seas respectively). The determination of γ values permit to simulate realistic sea conditions later on, in particular for determining extreme loads on floating structures in severe sea states.
The consistency of the fitting with respect to the actual sea state is subject to — at least — two key, connected aspects, which are: the frequency resolution (i.e., the spacing between two consecutive spectrum estimates) and the sampling error (i.e., the statistical variability of estimates due to both the finiteness of the wave record and the spectral averaging).
Based on realistic sea state spectral simulations, this work addresses the sensitivity of the JONSWAP fitting to these aspects and shows that it systematically results in a bias in the peakedness estimate — the bias being aggravated when the sampling error is large for a given signal length (from 10min to 1h). It is shown, in particular, that the error committed with respect to the true γ value is generally higher than 5% for most types of peaks and may often exceed 30%.
The aim of this work is to emphasize this issue for practical offshore and oceanographic applications for it may, in turn, potentially introduce a bias in the dynamic response of floating structures in numerical simulations and tank tests.
Improvements in Heavy Topside Installation Onto Spar Hull by Catamaran Floatover Method
Authors: Luo Michael Y. H. , Edelson David , Wan Jianan (Jay) , Sun Jiulong , Hassanaliaragh Sina 
Published: November 2013

The Murphy Kikeh Spar in Malaysia was the first Spar to employ a catamaran floatover method to install the topsides onto the Spar hull at the platform offshore location. The single column hull of the Spar dictates that the most practical way to float a topsides onto the Spar hull is by use of a catamaran system where the topsides structure forms a connection between the twin barges. For the Kikeh Spar the topside was first loaded out onto a single barge before being transferred to the catamaran system. The transfer operation was performed in sheltered waters. After the transfer and installation of the seafastening, the topside was towed to the installation site. The transfer of the topside weight was accomplished by deballasting the Spar and no quick release mechanism was used in the separation of the topside from the catamaran barges.
While the operations described were successfully implemented for the 4,000 MT Kikeh topside in a relative mild environment, improvements are recommended to perform this operation for heaver topsides in harsher environments such as the Gulf of Mexico.
This paper summarizes an internal study by Technip to extend and improve the floatover installation of Spar topsides to the Gulf of Mexico. This paper presents a step-by-step overview of an improved process for the installation of topsides having transportation weights of up to 25,000 ST. Similarities and improvements compared with Kikeh floatover installation will be discussed with particular focus on the following areas:
1. A new method of loading out of the topsides from the fabrication yard directly to the catamaran barges, requiring only one operation and eliminating the need for a transfer barge.
2. Specific Catamaran Ocean tow design and analysis considerations for the Gulf of Mexico. This addresses the effects of the harsher environment on the barges, grillage and topsides structure. A novel method of preloading the catamaran system is presented that reduces or, in some instances, eliminates the requirement for additional topside steel weight to accommodate additional motion-induced dynamic loads on the catamaran system during the ocean tow. The preloading also eliminates the risk associated with the operation of cutting tied-down braces.
3. A quick load release system is described which enables the rapid separation of the barges from the topside following the appropriate level of topside load transfer to the Spar hull.
Modifications of the PSA Regulations Based on Case Studies of Stability Accidents
Authors: Kvitrud Arne 
Published: November 2013

The paper describes available information about eight accidents worldwide related to the stability of petroleum units since 2000. A further seven stability incidents in Norway during the same period are also described. These accidents and incidents are used as cases for an evaluation of the existing Norwegian regulations on the stability of floating offshore petroleum units.
The accidents and incidents are grouped in categories based on the causes, and examples are given for each group.
The paper describes which Norwegian requirements could have prevented the accidents if they are complied with. Most of the accidents have involved deviations from the Norwegian regulations. Compliance with Norwegian regulations and (high-level) standards would cover most of the accident scenarios. However, some changes in the regulations have been found necessary. The paper describes these amendments, and the reasoning behind them.
Torpedo Piles: VH Capacity in Clay Using Resistance Envelope Equations
Authors: Kay S. 
Published: November 2013

This paper shows that torpedo pile in-place capacity under inclined VH load applied to the pile head can be reasonably assessed using simple modifications to resistance equations originally developed for straight-shafted circular caissons in clay under general vertical, lateral and moment (VHM) loading (Kay and Palix, 2010).
Also, the number of equations defining the VHM resistance envelope has been reduced from three to one. The resulting caisson yield function extends those currently available for surface and embedded foundations in clay under inclined load (e.g. DNV, 1992 and ISO, 2011).
Reliability of Buckle Formation Accounting for Bathymetry
Authors: Brunet Philippe , Oliphant John 
Published: November 2013

The mitigation of lateral buckling for subsea pipelines is achieved by making the pipe buckle at intended locations in preference to uncontrolled lateral buckles. At these engineered locations, the pipeline can be given enhanced characteristics (pipe tolerances, welds and Non-Destructive Examination (NDE) criteria). Alternatively, the buckle initiation equipment can be designed to distribute evenly the stress along the buckled pipeline and consequently reduce the maximum stress in the buckled pipeline section. As various parameters involved in the buckle formation process are uncertain (e.g. soil characteristics, residual horizontal imperfections after pipelay), a probabilistic approach is used to assess the likelihood that the pipeline will buckle at the intended locations.
Up to now, the existing guidelines focus on in-plane residual Out Of Straightness (OOS) whereas the impact of bathymetry (i.e. uneven seabed) is only addressed in a high level fashion, with no clear methodology.
The authors have therefore developed an original approach to account for the effects of bathymetry on the reliability of buckle formation. In a first step, the effects of bathymetry on buckle formation are discussed from a geotechnical and mechanical perspective. Then, the implementation of the buckling formation formulation in a probabilistic numerical subroutine is presented. Finally, a generic case study is considered to assess the impact of accounting for bathymetry on the buckle formation reliability analysis.
Research on the Arrangement of the Mooring Lines of the Thruster Assisted Mooring System
Authors: Zou Gang , Wang Lei , Zhang Feng 
Published: November 2013

As the offshore industry is developing into deeper and deeper water, station keeping technics are becoming more and more important to the industry. Based on the dynamic positioning system, the thruster assisted mooring system (TAMS) is developed, which consisted of mooring lines and thrusters.
The main function of the TAMS is to hold a structure against wind wave and current loads with its thruster and cables, which is mainly evaluated by the holding capacity of the system. The arrangement of the mooring lines (location of anchor or the mooring line angle relative to platform) will directly affect the TAMS holding capacity because of the influence of the directions of the mooring forces. So finding out an optimum arrangement of the mooring lines is essential since the performance of the TAMS depends greatly on the arrangement of the mooring lines. The TAMS of a semi-submersible platform, which is studied in this paper, consisted of eight mooring lines. By fixing the layout of the thrusters and changing the location of each mooring line for every case, the performances of the TAMS are analyzed. The platform motions, mooring line tensions and power consumptions are compared to obtain the optimum arrangement of mooring lines, and thus a thruster assisted mooring system with a better performance can be achieved. Time domain simulation is carried out in this paper to obtain the results.
Joint Environmental Data at Five European Offshore Sites for Design of Combined Wind and Wave Energy Devices
Authors: Li Lin , Gao Zhen , Moan Torgeir 
Published: November 2013

The costs for an offshore wind farm, especially with bottom fixed foundations increase significantly with increasing water depth. If costs can be reduced to a competitive level, the potential for wind farms in deep water is huge. One way of reducing costs might be to combine offshore wind with wave energy facilities at sites where these resources are concentrated.
In order to design combined renewable energy concepts, it is important to choose sites where both wind and wave energy resources are substantial. Such facilities might be designed in ultimate limit states based on load effects corresponding to 50-year wind and wave conditions. This requires a long-term joint probabilistic model for the wind and wave parameters at potential sites.
In this paper, five European offshore sites are selected for analysis and comparison of combined renewable energy concepts developed in the EU FP7 project – MARINA Platform. The five sites cover both shallow water (<100m) and deep water (> 200m), with three sites facing the Atlantic Ocean and the other two sites in the North Sea. The selection of the sites is carried out by considering average wind and wave energy resources, as well as extreme environmental conditions which indicate the cost of the system.
Long-term joint distributions of mean wind speed at 10-meter height (Uw), significant wave height (Hs) and spectral peak period (Tp) are presented for selected sites. Simultaneous hourly wind and wave hindcast data from 2001–2010 are used as a database, which are obtained from the National and Kapodistrian University of Athens.
The joint distributions are estimated by fitting analytical distributions to the hindcast data following a procedure suggested by Johannessen et al. (2001). The long-term joint distributions can be used to estimate the wind and wave power output from each combined concept, and to estimate the fatigue lifetime of the structure. For estimation of the wind and wave power separately, the marginal distributions of wind and wave are also provided.
Based on the joint distributions, contour surfaces are established for combined wind and wave parameters for which the probability of exceedance corresponds to a return period of 50 years. The design points on the 50-year contour surfaces are suggested for extreme response analysis of combined concepts. The analytical long-term distributions established could also be applied for design analysis of other offshore structures with similar environmental considerations of these sites.
Ship Security Analysis: The Effect of Ship Speed and Effective Lookout
Authors: Liwång Hans , Ringsberg Jonas W. 
Published: November 2013

The threat of piracy to commercial shipping is a concern for the protection and safeguarding of human lives, property and environment. Therefore, ships under piracy threat should follow security measures suggested by the International Maritime Organization (IMO) and the Contact Group on Piracy off the Coast of Somali. It is, therefore, important to choose the proper security measures for the right situation.
This study presents a simulation model that can be used for probabilistic risk assessments regarding the operation of commercial ships. This investigation specifically studies the pirate approach phase and quantifies the effect of ship speed and effective lookout. The purpose of introducing probabilistic risk assessment into the analysis of pirate attacks is to meet safety goals more effectively through a well-balanced combination of proactive and reactive measures whilst keeping focus on the intended over all purpose of the particular ship.
The study presents collected and documented knowledge regarding pirate capability, intention and likelihood to perform attacks. The knowledge is collected from experts with experience from the situation off the Horn of Africa. The collected information is input to an influence analysis that identifies the network of influences that govern the skiff approach. The simulation model describes piracy characteristics and decision making on the threatened ship, the characteristics and countermeasures of the ship under attack, as well as weather.
Based on a comparison with available statistics the overall conclusion of the work is that the threat analysis and the simulation model can quantify and explain how the studied risk control options affect the probability of a successful approach. The result therefore exemplifies how a quantified ship security analysis can support the recommendations in industry guidelines and also enable recommendations that to a greater extent can facilitate an educated decision by the ship operators.
Research Studies on Modeling Soil Erosion Caused by External Factors Near Offshore Structures
Authors: Shchemelinin Leonid G. , Sazonov Kirill E. , Denisov Valeriy I. 
Published: November 2013

For development of hydrocarbon deposits located in a shallow part of coastal shelf, offshore structures of gravitational type are widely used. The foundations of such structures are towed to sites where they are flooded and installed directly on sea bed. During operation of offshore structures the sea bed soil around and beneath the structure foundations are exposed to external effects such as sea currents, waves and also propeller streams generated by ships approaching the structures. As a result the soil is washed out from under the structure which may cause reduction of bearing surface area and even lead to loss of stability of the structure on seabed.
The model studies on soil erosion process near foundations of gravitational-type offshore platforms have been conducted at Krylov’s shallow water towing tank since 2000. This towing tank was not originally intended for such experiments, and, therefore, special experimental equipment has been developed for this purpose. These include a sandy bottom, current generation arrangements in the model test zone, instrumentation for measuring the bottom profile. Also specific model test procedures and methods for research on soil scour near the test objects have been developed and verified.
The paper gives a review of these research studies at the Krylov Centre, describe the test equipment, modeling techniques and test data scaling procedures as well as the experience learned from the experiments.
The paper gives some results of research studies of soil erosion near the foundations of offshore structures as a result of influence from sea currents and waves with coincident directions, and also as a result of influence from propeller streams of moored tankers and supply vessels.
The paper presents the model test results regarding the efficiency of a mobile system developed for soil erosion protection near the offshore structure intended for exploratory drilling in shallow waters of the Gulf of Ob in the Kara Sea.
A review of the recent Krylov’s studies in this field of research is given.