bluuebunny/crossref_metadata_2025 huggingface dataset:
Safety of Remote Magnetic Navigation in Patients With Pacemakers and Implanted Cardioverter Defibrillators
Authors: EITEL CHARLOTTE , HINDRICKS GERHARD , SOMMER PHILIPP , WETZEL ULRIKE , BOLLMANN ANDREAS , GASPAR THOMAS , PIORKOWSKI CHRISTOPHER , ARYA ARASH
Published: April 2010

Magnetic Navigation and Implanted Devices. Background: Remote magnetic catheter navigation (MNS) has been shown to be feasible and safe for radiofrequency catheter ablation of various cardiac arrhythmias. However, its safety in patients with implanted pacemakers or cardioverter–defibrillators has not yet been studied.

Objectives: This retrospective case series study intends to assess the acute and short‐term safety of remote MNS in patients with implanted pacemakers or cardioverter–defibrillators.

Methods: Between January 2008 and June 2009, a total of 31 patients with implanted pacemakers (n = 5) or cardioverter–defibrillators (n = 26) underwent 32 catheter ablation procedures using the remote MNS. Baseline pacing thresholds, sensed amplitudes, pacing and, if available, shock impedances as well as battery status were measured in all devices before, immediately after, and 1–3 months after catheter ablation.

Results: After ablation, no statistically significant difference in atrial sensing (2.7 ± 1.5 mV vs 3.1 ± 1.9 mV, P = 0.18) and impedance (457 ± 104 Ω vs 449 ± 101 Ω, P = 0.37) were observed. After ablation, no statistically significant difference in right ventricular sensing (10.4 ± 3.8 mV vs 10.9 ± 4.9 mV, P = 0.43) and impedance (535 ± 118 Ω vs 534 ± 120 Ω, P = 0.913) were observed. No changes in pacing threshold could be observed in all but 2 patients with biventricular cardioverter–defibrillators who underwent ventricular tachycardia ablation in lateral wall of left ventricle near the implanted epicardial electrode.

Conclusions: Ablation procedures using remote MNS can be performed safely in patients with implanted devices with no significant effects on device system integrity. Long endocardial ablation close to the insertion site of the implanted epicardial left ventricular leads can affect the pacing and/or sensing characteristics of these electrodes. (J Cardiovasc Electrophysiol, Vol. 21, pp. 1130‐1135)
Effect of Gadolinium on the Structure and Magnetic Properties of Glass and Glass–Ceramic Sillenites
Authors: Simon Simion , Udvar Alexandru D.
Published: April 2010

Glass samples belonging to xGd2O3·(1−x)[0.857Bi2O3·0.143GeO2] system, with 0.005≤x≤0.1, have been prepared by the rapid quenching method. Glass–ceramics were obtained after heat treatment of the as‐prepared glasses at 600°C for 24 h. All samples have been structurally characterized by X‐ray diffraction and electron paramagnetic resonance (EPR) spectroscopy. All as‐prepared samples are noncrystalline. The glass–ceramics contain different bismuthate crystalline phases, Bi12GeO20, BiLa type, and Bi24GeO38, depending on the gadolinium content in the glassy sample. The magnetic properties have been investigated by EPR and magnetic susceptibility measurements. The EPR and magnetic susceptibility data suggest that besides homogeneously distributed Gd3+ ions, both in the glass and glass–ceramic samples, there are clustered Gd3+ ions experiencing antiferromagnetic interactions.
Upconversion Luminescence of Ho3+–Tm3+ Codoped Chalcohalide Glasses and the Relevant Energy Transfer Mechanism
Authors: Wang Wei , Zhang Qiang , Xu Yinsheng , Shen Ce , Chen Danping , Chen Guorong
Published: April 2010

Ho3+–Tm3+‐codoped GeS2–Ga2S3–CsCl chalcohalide glasses are prepared and their upconversion (UC) show that the green UC luminescence from Ho3+ ions under an 808 nm diode laser excitation is considerably enhanced by Tm3+ ions codoping while the red UC luminescence from Tm3+ ions is weakened. The relevant mechanism is analyzed with respect to the energy transfer mechanism from Tm3+ ions to Ho3+ ions due to some energy levels of the Ho3+ ions is close to that of the Tm3+ ions.
Antimony Tuned Rhombohedral‐Orthorhombic Phase Transition and Enhanced Piezoelectric Properties in Sodium Potassium Niobate
Authors: Zuo Ruzhong , Fu Jian , Lv Danya , Liu Yi
Published: April 2010

It has been reported that the rhombohedral–orthorhombic low‐temperature polymorphic phase transition in (Na,K)NbO3 can be tuned close to room temperature by substituting Sb for Nb, such that enhanced piezoelectric properties are induced based on the theory of two‐phase coexistence. A diagram of phase structures changing with Sb content and temperature has been generalized for (Na,K)(Nb,Sb)O3 (NKNS) compositions. The thermal stability of piezoelectric properties of NKNS ceramics was evaluated considering the existence of successive phase transition above room temperature. The microstructure, dielectric, and ferroelectric properties of NKNS ceramics were discussed from a crystallographic point of view.
Low‐Temperature Processing of Silicon Oxycarbide‐Bonded Silicon Carbide
Authors: Eom Jung‐Hye , Kim Young‐Wook
Published: April 2010

Silicon oxycarbide (SiOC)‐bonded SiC ceramics were fabricated from SiC–polysiloxane mixtures at temperatures as low as 700°–900°C using a simple pressing and heat‐treatment process. During heat treatment, the polysiloxane transformed to an amorphous SiOC phase, which acted as the bonding material between SiC particles. The SiOC‐bonded SiC ceramics obtained had 18%–24% residual porosity and a flexural strength of 32–82 MPa depending on the starting SiC particle size and heat‐treatment temperature.
Agrifood supply chain, private‐sector standards, and farmers' health: evidence from Kenya
Authors: Asfaw Solomon , Mithöfer Dagmar , Waibel Hermann
Published: April 2010

This article evaluates the impact of adoption of European Union (EU) private‐sector standards on farmers' health in rural Kenya. The study utilizes cross‐sectional farm household‐level data collected in 2006 from a randomly selected sample of 439 small‐scale export farmers. We estimate the casual impact by utilizing a two‐stage Poisson regression model, two‐stage standard treatment effect model, as well as by regression based on propensity score, to assess the robustness of the results. Using these techniques, we demonstrate that the pesticide‐ascribed incidence of acute illness symptoms and the associated cost of illness significantly decrease with the adoption of standards. Ceteris paribus, farmers who adopt standards experience 70% lesser incidence of acute illness and spent about 50–60% less on restoring their health than nonadopters. Although standards can potentially prevent resource‐poor smallholders from maintaining their position in lucrative export markets, they can also result in positive changes in the health of those farmers who do adopt them, as shown by these results. This implies that, if adopted on a large scale, standards may reduce production externalities, corroborating the view that they may serve as a catalyst to transform production systems in developing countries.
Growth dynamics of dairy processing firms in the European Union
Authors: Gardebroek Cornelis , Turi Kedir N. , Wijnands Jo H.M.
Published: April 2010

The structure of the dairy processing industry in the European Union has changed enormously in recent decades. In many countries, the industry is characterized by a few large companies with a big market share accompanied by many small processors that often produce for niche markets. This article investigates which factors relate to growth of dairy processing firms. Using a unique 10‐year panel data set and recently developed dynamic panel data estimators, the growth process of dairy processors is investigated for six rather diverse European countries. The data structure and the estimation method allow for dealing with endogeneity issues in an appropriate way. Firm size growth measured in total assets is found to be affected by firm size, firm age, and financial variables. Growth in number of employees is only affected by firm age and lagged labor productivity. Implications for these results are given in the final section of the article.
Food aid allocation policies: coordination and responsiveness to recipient country needs
Authors: Kuhlgatz Christian , Abdulai Awudu , Barrett Christopher B.
Published: April 2010

We employ censored least absolute deviations and multivariate Tobit estimators to investigate whether food aid flows from the main donor countries respond to recipient country needs as reflected in low food availability, low income, or both. We also explore the hypothesis that donor countries specifically coordinate their food aid shipments to recipient countries. Our findings show that food aid in aggregate and from each donor is significantly targeted at poorer countries and is highly persistent over time. Food aid responses to food availability shortfalls, natural disasters, and violent conflicts are common but more modest and uneven across donors. Finally, we find strong evidence of donor coordination in food aid allocation.
Acute treatment of a concomitant horizontal root fracture and luxation of the coronal fragment of the right upper central incisor: a case report
Authors: Berrezouga Latifa , Belkhir Chems , Jbir Ridha , Belkhir Mohamed Semir
Published: April 2010

Abstract –  We report a case of a horizontal intra‐alveolar root fracture between the middle and apical third of the upper right central incisor associated with an extrusive luxation of the coronal fragment, in a 24‐year‐old male patient. Twenty minutes after being accidentally hit by a metallic device, the patient’s coronal portion was repositioned and splinted under local anesthesia. After that, we lost sight of the patient. One year later, the patient showed up. The splint was lost, the tooth showed physiological mobility and responded to pulp testing. Radiographs showed healing of the horizontal fracture and normal periodontal ligament.
Sleep patterns, electronic media exposure and daytime sleep‐related behaviours among Israeli adolescents
Authors: Shochat Tamar , Flint‐Bretler Ofra , Tzischinsky Orna
Published: April 2010

Aim:  The aim of this study was to assess weekday and weekend sleep patterns and their relationships with electronic media (television and computer) exposure and with daytime sleep‐related behaviours, including sleep problem behaviours, sleepiness and fatigue in Israeli adolescents.

Methods:  A cross‐sectional survey, which includes 470 8th and 9th grade middle school students (mean age 14 ± 0.8) in the normative school system, was performed. Students completed the modified School Sleep Habits Survey (SSHS), and the modified Electronic Media and Fatigue Questionnaire (EMFQ).

Results:  Adolescents went to bed at 23:00 and 01:45 hours, and slept <7.5 and nearly 10.0 h on average, during weekdays and weekends respectively. Average electronic media exposure per day was about 3 h for television and 2.5 h for internet. Adolescents with a bedroom television went to bed later, had longer sleep latency and slept less than those without a bedroom television. Increased electronic media exposure and poor daytime sleep‐related behaviours predicted later bedtime, longer sleep latency during weekdays and later wake‐up time during weekends.

Conclusion:  Poor sleep patterns in Israeli adolescents are related to excessive electronic media habits and daytime sleep‐related problems. These findings raise a public health concern regarding lifestyle and functioning in young individuals.
Strategic Tax and Financial Reporting Decisions: Theory and Evidence*
Authors: MILLS LILLIAN F. , SANSING RICHARD C.
Published: April 2010

This paper examines the effect of book‐tax differences on the probability that a transaction is audited and the probability that additional taxes are collected. It constructs a stylized model in which the taxpayer reports both financial accounting income and taxable income. The government observes both reports before deciding whether to conduct an audit. The analysis of the equilibrium yields two hypotheses. First, the probability that the government will audit a transaction is higher if the transaction generates a positive book‐tax difference (e.g., an expenditure that is deducted for tax purposes but capitalized for financial reporting purposes) than if the transaction generates no book‐tax difference. Second, conditional on being selected for audit, transactions with and without book‐tax differences are equally likely to have detected understatements of tax liability.

These hypotheses are tested using Internal Revenue Service (IRS) data from the Coordinated Examination Program. The empirical tests are consistent with the predictions of the strategic tax compliance model.
Predictive mapping of season distributions of large mammals using GIS: an application to elephants on Mount Kenya
Authors: Vanleeuwe Hilde
Published: April 2010

1. Knowledge of elephants in forested environments where visibility is poor is often restricted to elephant density estimates derived from counts of elephant dung piles along line transects. Elephant dung piles are a good indicator of elephant habitat use over a period of time (i.e. a season) because they remain visible for several months. Using Mount Kenya (MK) in Kenya as a case study, we demonstrate how those dung pile counts can additionally be used to develop elephant dung pile explanatory models and distribution maps.

2. The dung pile explanatory models are built from a selected number of line‐transect samples per season using generalized linear model analysis, in which the counted dung of each sample is explained by the combined effects of a series of environmental and anthropomorphic parameters. For the significant explanatory parameters in the models, digital map layers are developed and integrated into a geographic information system. Applying the explanatory models, predictive seasonal elephant dung pile distribution maps are developed.

3. Data preparation and analysis are intensive, but the distribution maps derived from explanatory parameters of distribution are a powerful tool for patrol planning and land‐use management and to locate areas of high elephant density and the habitats they move between. This method is useful for sites where physical, environmental, logistical or other constraints render it impossible to spread line transects evenly over the entire study area, assuming that transects are representative samples of the entire habitat.
A Framework for Discrete-Time H2 Preview Control
Authors: Hazell A. J. , Limebeer D. J. N.
Published: April 2010

The purpose of this paper is to provide a set of synthesis and design tools for a wide class of H2 preview control systems. A generic preview design problem, which features both previewable and nonpreviewable disturbances, is embedded in a standard generalized regulator framework. Preview regulation is accomplished by a two-degrees-of-freedom output-feedback controller. A number of theoretical issues are studied, including the efficient solution of the standard H2 full-information Riccati equation and the efficient evaluation of the full-information preview gain matrices. The full-information problem is then extended to include the efficient implementation of the output-feedback controller. The synthesis of feedforward controllers with preview is analyzed as a special case—this problem is of interest to designers who wish to introduce preview as a separate part of a system design. The way in which preview reduces the H2-norm of the closed-loop system is analyzed in detail. Closed-loop norm reduction formulas provide a systematic way of establishing how much preview is required to solve a particular problem, and determine when extending the preview horizon will not produce worthwhile benefits. The paper concludes with a summary of the main features of preview control, as well as some controller design insights. New application examples are introduced by reference.
Position-Error Based Schemes for Bilateral Teleoperation With Time Delay: Theory and Experiments
Authors: Polushin Ilia G. , Liu Peter X. , Lung Chung-Horng , On Gia Dien
Published: April 2010

The problem of stable bilateral teleoperation with position-error based force feedback in the presence of time-varying possibly unbounded communication delay is addressed. Two stabilization schemes are proposed that guarantee “independent of delay” stability of the teleoperator system. In particular, one of the schemes theoretically allows to achieve an arbitrary high force-reflection gain, which leads to better transparency without sacrificing the stability of the overall system. The stability analysis is based on the input-to-output stable small gain theorem for systems of functional-differential equations. Experimental results are presented, which demonstrate stable behavior of the telerobotic system with time-varying communication delay during contact with a rigid obstacle.
Brachistochrone on a 1D Curved Surface Using Optimal Control
Authors: Hennessey Michael P. , Shakiban Cheri
Published: April 2010

The brachistochrone for a steerable particle moving on a 1D curved surface in a gravity field is solved using an optimal control formulation with state feedback. The process begins with a derivation of a fourth-order open-loop plant model with the system input being the body yaw rate. Solving for the minimum-time control law entails introducing four costates and solving the Euler–Lagrange equations, with the Hamiltonian being stationary with respect to the control. Also, since the system is autonomous, the Hamiltonian must be zero. A two-point boundary value problem results with a transversality condition, and its solution requires iteration of the initial bearing angle so the integrated trajectory runs through the final point. For this choice of control, the Legendre–Clebsch necessary condition is not satisfied. However, the k=1 generalized Legendre–Clebsch necessary condition from singular control theory is satisfied for all numerical simulations performed, and optimality is assured. Simulations in MATLAB® exercise the theory developed and illustrate application such as to ski racing and minimizing travel time over either a concave or undulating surface when starting from rest. Lastly, a control law singularity in particle speed is overcome numerically.
Design of Gain-Scheduled Strictly Positive Real Controllers Using Numerical Optimization for Flexible Robotic Systems
Authors: Forbes James Richard , Damaren Christopher John
Published: April 2010

The design of gain-scheduled strictly positive real (SPR) controllers using numerical optimization is considered. Our motivation is robust, yet accurate motion control of flexible robotic systems via the passivity theorem. It is proven that a family of very strictly passive compensators scheduled via time- or state-dependent scheduling signals is also very strictly passive. Two optimization problems are posed; we first present a simple method to optimize the linear SPR controllers, which compose the gain-scheduled controller. Second, we formulate the optimization problem associated with the gain-scheduled controller itself. Restricting our investigation to time-dependent scheduling signals, the signals are parameterized, and the optimization objective function seeks to find the form of the scheduling signals, which minimizes a combination of the manipulator tip tracking error and the control effort. A numerical example employing a two-link flexible manipulator is used to demonstrate the effectiveness of the optimal gain-scheduling algorithm. The closed-loop system performance is improved, and it is shown that the optimal scheduling signals are not necessarily linear.
Wnt Proteins Promote Bone Regeneration
Authors: Minear Steven , Leucht Philipp , Jiang Jie , Liu Bo , Zeng Arial , Fuerer Christophe , Nusse Roel , Helms Jill A.
Published: April 2010

A liposome-encased ligand for the Wnt signaling pathway can accelerate bone regeneration after injury.
Cenozoic paleobotany of the John Day Basin, central Oregon
Authors: Dillhoff Richard M. , Dillhoff Thomas A. , Dunn Regan E. , Myers Jeffrey A. , Strömberg Caroline A. E.
Published: April 2010

The John Day Basin of central Oregon contains a remarkably detailed and well-dated Early Eocene–Late Miocene sedimentary sequence, known for its superb fossils. This field trip examines plant fossil assemblages from throughout the sequence in the context of their geological and taphonomic setting and regional and global significance. The Early to Late Eocene (>54–39.7 Ma) Clarno Formation contains fossil plants and animals that occupied an active volcanic landscape near sea level, interspersed with meandering rivers and lakes. Clarno assemblages, including the ca. 44 Ma Nut Beds flora, record near-tropical “Boreotropical” rainforest, which was replaced during late Clarno time by more open and seasonal subtropical forest. The overlying John Day Formation (39.7–18.2 Ma) was deposited in a backarc landscape of low hills dotted with lakes and showered by ashfalls from the Western Cascades. Fossils and paleosols record the advent of the “Icehouse” Earth during the earliest Oligocene, with decreasing winter temperature and more seasonal rainfall that supported open deciduous and coniferous forest, much like that of the southern Chinese highlands today. Sixteen and a half million years ago the Picture Gorge flood basalt covered the region. Animals and plants fossilized in the overlying (ca. 16 to >12 Ma) Mascall Formation occupied a relatively flat landscape during a warm and moist period known as the Middle Miocene Climatic Optimum. In total this sequence preserves a detailed series of time slices illustrating regional biotic and landscape evolution during the Cenozoic that is highly relevant for deciphering regional and global biotic, climatic, and geological trends.
Paleo-landslides in the Tyee Formation and highway construction, central Oregon Coast Range
Authors: Hammond Charles M. , Meier Dan , Beckstrand Darren
Published: April 2010

Investigation and design-build construction of the Highway 20 realignment through the Oregon Coast Range provides new insight into paleo-landslides of the Tyee Formation and their slope stability. They are widespread, often extending outside of current drainage basins, and much of their morphology has been almost completely hidden by surficial processes. Radiocarbon tests indicate that some of the slide features are older than the testing limits, while other results range from approximately 18,000 to 40,000 yr B.P. The depth of erosion suggests that the paleo-slides may be as old as Pliocene.

Geotechnical models of the paleo-slides, needed to analyze potential construction impacts, are developed from subsurface explorations, construction outcrops, radiocarbon testing, monitoring of geotechnical instruments, and geomorphology revealed by light detection and ranging (LIDAR). The process of predicting landslide boundaries (head scarps, toes, lateral and basal shear zones, etc.) for stability analysis of specific landslides has revealed details of their geologic evolution. This field trip provides background on (a) the investigations that have exposed numerous giant paleo-landslides, (b) findings and interpretations of the age of the landslides and (c) methods that are being employed to mitigate landslide reactivation.
GRAVITOMAGNETISM IN TELEPARALLEL GRAVITY
Authors: SPANIOL E. P. , DE ANDRADE V. C.
Published: April 2010

The assumption that matter charges and currents could generate fields, which are called, in analogy with electromagnetism, gravitoeletric and gravitomagnetic fields, dating from the origins of General Relativity (GR). On the other hand, the Teleparallel Equivalent of GR (TEGR), as a gauge theory, seems to be the ideal scenario to define these fields, based on the gauge field strength components. The purpose of the present work is to investigate the nature of the gravitational electric and magnetic fields in the context of the TEGR, where the tetrad formalism on which it is based seems more suited to deal with phenomena related to observers. As its applications, we have studied the gravito-electromagnetic fields for the Schwarzschild solution and for the geometry produced by a spherical rotating shell in slow motion and weak field regime. The expressions obtained, at the linear regime, are very similar to those of electromagnetism.
Sequence stratigraphic and depositional framework of the Cenozoic fill, Central and Northern North Sea Basin
Authors: GALLOWAY W. E. , GARBER J. L. , LIU XIJIN , SLOAN B. J.
Published: April 2010

The post-Danian through Miocene clastic fill of the Central and Northern North Sea Basin consists of four tectonosequences that record the regional structural evolution of the basin and adjacent source areas. The tectonosequences, in turn, contain strata deposited during at least 15 depositional episodes, creating a series of stratigraphic sequences bounded by condensed sections and/or erosion surfaces. The Paleocene tectonosequence records six depositional episodes and was initiated by fault movement coupled with source area uplift. Proximal delta-fed submarine aprons of the Maureen and Andrew episodes were subsequently overridden by the Forties/Dornoch braid-delta system. Widespread source area and basin-margin foundering terminated the Paleocene with regional flooding and deposition of the Balder condensed section. Mass wasting of the relict shelf margins locally redeposited Paleocene sediments as turbidite and slump lobes. The Eocene tectonosequence began with the Frigg depositional episode. A combination of steep shelf gradient and high marine energy flux bypassed shelf sediment to the Viking trough. Subsequently four shelf progradational episodes terminated with pulsed latest Eocene shelf-margin offlap driven by stepwise relative sea-level fall. Oligocene and Miocene tectonosequences encompass four eposides of basin filling. Sediments deposited in shelf and deep-marine settings were increasingly reworked by geostrophic currents, culminating in accumulation of large Miocene contourite drift complexes along the basin axis.
The geology of the Gryphon Oil Field
Authors: NEWMAN M. St. J. , REEDER M. L. , WOODRUFF A. H. W. , HATTON I. R.
Published: April 2010

The Gryphon Oil Field is located 320 km northeast of Aberdeen in UK Ninth Round Block 9/18b. The field was discovered by Well 9/18b-7 in 1987. This well proved the prognosed Eocene/Paleocene submarine fan system.

To date, Kerr-McGee has drilled 13 wells and 10 sidetracks on the field. In 1990 a 3D seismic survey was acquired over the whole trend, in Blocks 9/18a, 9/18b, 9/23a and 9/23b.

The field is a complex combination structural/stratigraphic trap formed on the northerly plunging nose of the Crawford Ridge. The principal reservoir sands are of the Balder Formation (latest Paleocene-earliest Eocene) and consist of thick, massive, well-sorted, high porosity sands deposited from high-density gravity flows. Water-escape and soft sediment deformation features are common and no primary sedimentary structures are preserved. These sands formed a 'Lowstand Fan' complex within a lowstand systems tract. Areas of sand deposition were determined by the sea floor topography, which was controlled by basement structure, soft sediment deformation and the disposition of older sandbodies.

In order to establish accurate time lines, it is important to identify the relative ages of these sands correctly. This was achieved using detailed biostratigraphy combined with the innovative techniques of 'desanding' and petrophysical analysis of the Balder Tuff.

Overlying the Balder sequence is the earliest Eocene interbedded claystone, silt and sand sequence of the Frigg Formation. These sediments were deposited within the 'Lowstand Wedge' channel/levee complex which built out across the previously deposited Balder Fan.

Oil and gas migrated into the structure via the ridge fault system from the mature Kimmeridge Clay source in the deep graben to the north and east.
Middle to Late Jurassic basin evolution and sandstone reservoir distribution in the Danish Central Trough
Authors: JOHANNESSEN P. N. , ANDSBJERG J.
Published: April 2010

During the Mid- to Late Jurassic, long-term eustatic sea-level rise and half-graben subsidence in the Danish Central Trough resulted in a major transgression. Deposition of widespread alluvial plain sediments in the Søgne Basin and Tail End Graben was terminated in the Late Bathonian due to bypass and erosion following a short-term relative sea-level fall. The sea-level fall was followed by a relative sea-level rise during the Callovian which caused the development of a transgressive succession of coastal plain and shallow marine deposits. The transgressive succession consists of several prograding sediment wedges commonly terminated by a coal bed and a flooding surface. As transgression continued during the Late Jurassic, the shoreline shifted westwards. Transgressive Oxfordian shoreface to back-barrier sandstones were deposited. Another short-term relative sea-level fall occurred during the Kimmeridgian during which regressive shoreface to beach sandstones were deposited. During the Late Kimmeridgian and Volgian, the long-term relative sea-level rise resulted in deposition of thick Volgian offshore claystones in the central part of the Central Trough (Heno Plateau, Gertrud Graben and Feda Graben). During the Volgian and Early Cretaceous, the transgression continued towards the west and shallow marine sandstones may have been deposited along the western margin of the Central Trough fringing the Mid North Sea High (Grensen Nose Basin and Outer Rough Basin). Along the Ringkøbing Fyn High in the easternmost part of the Central Trough, Volgian and Early Cretaceous fan-delta sandstones and basin floor turbidite sandstones are interstratified with offshore claystones.
Physical modelling of North Sea salt diapirism
Authors: WESTON P. J. , DAVISON I. , INSLEY M. W.
Published: April 2010

Scaled analogue models provide a powerful tool for investigating progressive deformation. By varying experimental parameters it is possible to produce a wide variety of diapir morphologies and overburden responses.

This paper describes the results of one of a series of experiments which investigates the geometry of overburden sediments around diapirs. The roles of basement faulting and differential sediment loading in the growth of diapirs are assessed. The template for this experiment is provided by analysis of a regional seismic line across the Central Graben of the North Sea.

The model produced two diapir types which formed in different ways. Type 1 diapirs are initiated by a large fault smearing the salt along the fault plane which creates a path for later upward migration of salt to produce small diapiric walls. Type 2 diapirs can be triggered by either tectonic or sedimentary differential loading. They are predicted to be longer lived and more voluminous than Type 1 diapirs and will tend to form isolated circular structures.
F15-A: a Triassic gas field on the eastern limit of the Dutch Central Graben
Authors: FONTAINE J. M. , GUASTELLA G. , JOUAULT P. , de la VEGA P.
Published: April 2010

The F15-A gas field lies at the eastern margin of the Dutch Central Graben, the reservoirs being found within the overpressured Triassic Main Buntsandstein Formation. The discovery well, F15-4, was drilled in 1985 and was subsequently followed by the two appraisal wells, F15-5 and F15-7. Structurally speaking, the F15 area is located in an intermediate structural compartment between the Central Graben, to the west and the Schill Grund High, to the east. The structure consists of a NNE–SSW-trending turtle back anticline, plunging to the south, with gently dipping flanks to the east and west. Northwards, closure is provided by a NW–SE-oriented erosional trough which cuts deeply into the Lower Triassic and is filled by Upper Triassic/Jurassic sediments.

The primary reservoir is the Volpriehausen Sandstone Member, which is very fine to coarse grained and irregularly cemented by dolomite, anhydrite and halite. Four lithofacies have been recognized: dunal, interdunal, ephemeral fluviatile (distal wadi) and playa-lake related. These facies show a coarsening-upward profile, caused by the successive depositional environments becoming increasingly arid as they grade from playa lake to dunes. A seismic amplitude study was carried out, based on the links between porosity and seismic response at the reservoir level, to identify the areas with the best potential reservoir development.

The field was originally identified and discovered on the basis of two-dimensional seismic data; however, a three-dimensional survey was subsequently shot and has increased the confidence in the structural interpretation. Based on this, one horizontal production well will be drilled in order to put the field on stream in June 1993.
A review of the Triassic play in the Roer Valley Graben, SE onshore Netherlands
Authors: WINSTANLEY A. M.
Published: April 2010

The Roer Valley Graben is a NW-trending fault-bounded graben marking the eastern limit of the Sole Pit/West Netherlands basins. Sedimentation is composed of four megasequences. The first is a broadly regressive Carboniferous (Visean to Stephanian) sequence which is terminated by the Saalian Unconformity. This is followed by a Zechstein to Middle Jurassic megasequence comprising marine fringe facies and alluvial clastics which grade upwards into open marine sediments of Middle Jurassic age. Megasequence three is composed of syn-rift Upper Jurassic deltaics and is very sparsely preserved due to inversion-related erosion. The final megasequence is composed of post-rift Upper Cretaceous chalk and Tertiary clastics. A major inversion occurred during the Maastrichtian and subsequent erosion removed all the chalk (up to 1000 m) from the graben area but left the sequence on the flanks largely unaffected.

Tectonic development of the basin is dominated by the Late Jurassic rifting phase. This was largely extensional; however, a component of oblique-slip motion is evident and is responsible for the intersecting pattern of N–S- and more NW–SE-trending faults. This structural fabric was subsequently overprinted by NW-trending Cretaceous inversion structures.

Alluvial fan sandstones within the Main Buntsandstein and Röt formations are the primary reservoir target. Repeated rejuvenation of early faults caused renewed influxes of sediments and stacking of the fan sequences. Subsequent diagenesis, primarily associated with the rifting phase, has reduced porosities and permeabilities.

The source rocks for this play are the Westphalian and Namurian coals and shales. These are gently folded and subcrop to the Zechstein-Upper Jurassic sequence across the graben. Peak generation is estimated to have occurred in Early to Late Cretaceous times, prior to the main period of inversion which effectively shut off hydrocarbon generation over much of the basin.

Trap development was initiated during the Early Jurassic and developed further throughout the Late Jurassic rifting phase. However, substantial modifications occurred as a result of the Cretaceous inversion and, more locally, relaxation of the graben during the Tertiary.

The two discoveries at Waalwijk are early rift (Early Jurassic) tilted fault block structures, which were modified during the Cretaceous inversions. Oil and gas charges followed each other into the reservoirs, with gas probably displacing the oil. Other tested trap types include both pure inversion and inverted rift structures. The latter trap type has met with some success, whereas all wells on the former have been dry to date.

The overall success rate for the area is good but not as high as that achieved in the offshore extension of the play fairway. This is primarily a function of the Cretaceous inversion of the Roer Valley Graben which not only downgraded trap integrity and reservoir quality but also shut off hydrocarbon generation.
Permo-Carboniferous and older plays, their historical development and future potential
Authors: GÉRARD J. , WHEATLEY T. J. , RITCHIE J. S. , SULLIVAN M. , BASSETT M. G.
Published: April 2010

The plays reviewed in this paper are those developed where Permian and older organic-rich rocks have been preserved. These have sourced approximately 60 × 109 barrels of oil equivalent in the area under consideration, in oil, gas and oil shale developments, and range in age from the Cambrian to Permian. They were deposited in marine to terrestrial environments, and their development was controlled by the evolution of life forms, changes of relative sea-level and the plate tectonic configuration of the depocentres. Clastic and carbonate reservoir distribution was controlled by tectonic phases and relative sea-level variations. Trapping is by both structural and stratigraphic mechanisms. Preservation of source and reservoir potential is dependent on a lack of intense orogenic activity and should, therefore, be sought away from zones of intense tectonism that post-date potential source rocks.

Proven play types are extrapolated to under-explored areas where similar potential may exist, and the potential of methane extraction from coal beds is suggested.
The late Carboniferous ‘Barren Red Bed’ play of the Silver Pit area, Southern North Sea
Authors: BESLY B. M. , BURLEY S. D. , TURNER P.
Published: April 2010

A multidisciplinary study of the gas-bearing Westphalian red bed sequence of the Southern North Sea is presented. Comparison with analogous fades in Carboniferous sequences in the UK onshore and the eastern Netherlands suggests that two distinct alluvial red bed units are present, one of Westphalian C and one of Westphalian D age. Development of red pigment in these units was largely the result of contemporaneous pedogenesis. Interpretation of the stratigraphy is complicated by the widespread occurrence of reddening caused by penetrative weathering, both during the Carboniferous and related to the formation of the sub-Permian unconformity.

Gas reservoirs are present in sandstones in the Westphalian C red bed unit. This unit has higher net:gross ratios and better poroperm characteristics than the underlying Coal Measures. The better reservoir quality in the red bed unit is largely influenced by late diagenetic alteration related to hydrocarbon migration.

A sedimentological and diagenetic model for the formation of the Westphalian C red bed unit implies that this unit is likely to have a distinctive reservoir architecture, which, together with better reservoir qualities, distinguishes it from the hydrocarbon play in the underlying Coal Measures.
Controls on reservoir quality in the Triassic Sherwood Sandstone of the Irish Sea
Authors: MEADOWS N. S. , BEACH A.
Published: April 2010

The Lower Triassic Sherwood Sandstone Group constitutes the principal reservoir target in the East Irish Sea Basin. Interpretation of sedimentary facies allows recognition of major low sinuosity braided fluvial channel, minor ephemeral fluvial channel, aeolian dune and sandsheet, unconfined fluvial sheetflood and playa lake deposits that are discussed in terms of facies associations. Reservoir quality is highly variable, with porosity and permeability data revealing significant differences between fluvial, sheetflood and aeolian facies associations. The latter, in particular, preserve very high reservoir quality reflecting an open grain fabric and paucity of blocky cements. Variations in porosity between the facies associations relate primarily to the distribution of quartz cement which is significantly more abundant in fluvial channel sandstones than other facies. Authigenic illite, while severely limiting permeabilities in some reservoir zones, is not facies specific and does not contribute to the observed variations. It is suggested that the disparity in the abundance of quartz cement between facies associations relates to two distinct grain types that correlate broadly with fluvial and aeolian associations, respectively, and probably derive from different provenances. The evolution of the basin, in controlling the distribution of the major facies, influenced the distribution of the two grain populations and, thus, also the reservoir quality of the sandstones.
The Kish Bank Basin, offshore Ireland
Authors: NAYLOR D. , HAUGHEY N. , CLAYTON G. , GRAHAM J. R.
Published: April 2010

The Kish Bank Basin, a half-graben lying offshore only a few kilometres east and southeast of Dublin in the Irish Sea, is elongated northeast-southwest and measures approximately 48 × 32 km. The basin is bounded to the northwest and north by the Dalkey-Lambay fault system and to the southwest by the Bray Fault. A major dextral strike-slip fault, the northwest-trending Codling Fault, bisects the basin. Three wells have been drilled in the area: Amoco 33/22-1(1977), Shell 33/21-1(1979) and Fina 33/17-1(1986). The Amoco well penetrated a Carboniferous section on the southeastern rim of the basin (
Jenner 1981
), while the other two holes drilled the Permo-Triassic basin-fill sequence, but without reaching the base of the Permian. The Permo-Triassic succession is similar to that in the East Irish Sea Basin and includes thick Triassic salt sequences. SEM examination of sandstone samples from potential reservoir sections in the 33/21-1 well indicates good porosity in the cleaner sandstones. This is interpreted as largely secondary, following dissolution of early cements. Seismic studies suggest that up to 2.7 km of Jurassic (probably Liassic) strata are present against the western bounding faults.

Maturation studies have been carried out on material from two of the wells. The Silesian section penetrated by 33/22-1 ranges in age from Westphalian B to Westphalian D. It is of ‘coal measures’ facies and includes numerous seams of medium to high volatile bituminous coal. Much of the Westphalian section is mature with regard to gas generation, with vitrinite reflectance
(Rm)
values ranging from
c.
0.8% to 1.3%. Maturation levels in the Permo-Triassic section in 33/21-1 range from
c.
1.3%–1.6%
Rm,
suggesting that any underlying Westphalian rocks in deeper parts of the basin would be mature to marginally post-mature with respect to dry gas generation. The burial history of the basin, and the distribution of source rocks within it, are discussed.
The use of dipmeter logs in the structural interpretation and palaeocurrent analysis of Morecambe Fields, East Irish Sea Basin
Authors: COWAN G. , OTTESEN C. , STUART I. A.
Published: April 2010

Dipmeter logs have been processed in a variety of ways as an aid to understanding the geology of the North and South Morecambe Gas Fields. They have yielded high quality structural information which has contributed to understanding the structural configuration and tectonic history of these fields. Several faults have been identified, cutting well paths, and dipmeter analysis has allowed the correct orientation and direction of throw to be determined. In one well, the deviated well path has intersected each of two listric faults in two separate places, allowing unusually precise definition of these fault planes. Throughout the Ormskirk Sandstone Formation, the predominant palaeocurrent direction has been found to be towards the west or southwest. The most consistent palaeocurrent orientations were measured in intervals of planar cross-stratified channel-fill facies sandstones, but similar results, with greater scatter were observed in ephemeral channel sandstones facies. These consistent palaeocurrent results suggest that the East Irish Sea Basin formed a distinct depo-centre during Ormskirk sandstone times. The implication is that during the deposition of the Ormskirk Sandstone, palaeocurrents were controlled by a regional dip towards the Keys Fault. There are changes in palaeoflow from the base of the Ormskirk Sandstone Formation to the top (a vertical thickness of 800 ft), also changes from the southern to the northern ends of the field. In the underlying St Bees Sandstone Formation, consistent palaeocurrent directions proved more difficult to obtain, since major channel facies sandstones are rarer. No angular unconformity was observed between the St Bees and Ormskirk Sandstone formations. Within the Ormskirk Sandstone interval, however, very consistent, 1° to 2° changes in structural dip occur at the same stratigraphic levels in several wells and indicate small-scale tectonic rotations during the deposition of these sandstones. These are probably related to tectonic reactivation which has been invoked in previous literature to explain periodic rejuvenation of the depositional system during deposition of the reservoir sandstones. The fact that the observation of such small-scale adjustments can be repeated in several wells is an indication of the degree of precision of the results obtained from the dipmeter logs in these wells.
The southern West Greenland continental margin: rifting history, basin development, and petroleum potential
Authors: CHALMERS J. A. , PULVERTAFT T. C. R. , CHRISTIANSEN F. G. , LARSEN H. C. , LAURSEN K. H. , OTTESEN T. G.
Published: April 2010

The development of the continental margin of West Greenland is closely related to the processes that led to the opening of the Labrador Sea. The opening of the Labrador Sea began in the Early Paleocene (anomaly 27N), and not in the Late Cretaceous as previously supposed. Modelling of magnetic data and new interpretation of seismic data indicate that a large area previously regarded as underlain by oceanic crust is in fact underlain by block-faulted continental crust overlain by syn- and post-rift sedimentary sequences. The ocean–continent transition is now placed 100–150 km southwest of the foot of the continental slope instead of at the foot of this slope. Rifting in the Labrador Sea area began, however, in the Early Cretaceous. The earliest sediments are the syn-rift lower and upper members of the Bjarni Formation on the Labrador shelf and their likely equivalents, the pre- to syn-rift Kitsissut and Appat sequences on the Greenland margin. The age of these units is Barremian (or older) to Albian. The units are overlain by widespread mudstone-dominated units, the Markland Formation of the Labrador shelf and the Kangeq Sequence on the Greenland margin. The former is Cenomanian–Danian in age. By analogy the base of the Kangeq Sequence is probably Cenomanian (or Turonian), while the top is known from well ties to be at the Cretaceous–Tertiary boundary. Rifting was subdued during deposition of these mudstone units. Rifting was renewed in the Early Paleocene, and mudstones, siltstones and very fine sandstones were deposited. With the initiation of sea-floor spreading there was considerable igneous activity at the ocean–continent transition, as well as in the onshore area where picrites followed by plagioclase-porphyritic basalts were erupted. After the end of the Paleocene there was little rifting in the region, but compressional structures were formed locally as a response to transpression related to strike-slip movements that transferred plate motion from the Labrador Sea to Baffin Bay. A marked Early Oligocene unconformity separates the syn-drift Paleocene–Eocene succession from the post-drift middle Oligocene–Quaternary sediments. Sediments deposited since the Paleocene are dominated by sands. The main hydrocarbon play types offshore West Greenland are related to tilted fault blocks. Source rocks are anticipated near the base of the Kangeq Sequence, which is also the seal, and reservoirs are sandstones in the Appat and Kitsissut sequences. These two sequences were not reached by any of the exploration wells drilled in the 1970s.