bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of dose reduction on the detection of mammographic lesions: A mathematical observer model analysis
Authors: Chawla Amarpreet S. , Samei Ehsan , Saunders Robert , Abbey Craig , Delong David
Published: August 2007

The effect of reduction in dose levels normally used in mammographic screening procedures on the detection of breast lesions were analyzed. Four types of breast lesions were simulated and inserted into clinically‐acquired digital mammograms. Dose reduction by 50% and 75% of the original clinically‐relevant exposure levels were simulated by adding corresponding simulated noise into the original mammograms. The mammograms were converted into luminance values corresponding to those displayed on a clinical soft‐copy display station and subsequently analyzed by Laguerre‐Gauss and Gabor channelized Hotelling observer models for differences in detectability performance with reduction in radiation dose. Performance was measured under a signal known exactly but variable detection task paradigm in terms of receiver operating characteristics (ROC) curves and area under the ROC curves. The results suggested that luminance mapping of digital mammograms affects performance of model observers. Reduction in dose levels by 50% lowered the detectability of masses with borderline statistical significance. Dose reduction did not have a statistically significant effect on detection of microcalcifications. The model results indicate that there is room for optimization of dose level in mammographic screening procedures.
Evaluation of three types of reference image data for external beam radiotherapy target localization using digital tomosynthesis (DTS)
Authors: Godfrey Devon J. , Ren Lei , Yan Hui , Wu Q. , Yoo Sua , Oldham M. , Yin Fang Fang
Published: August 2007

Digital tomosynthesis (DTS) is a fast, low‐dose three‐dimensional (3D) imaging approach which yields slice images with excellent in‐plane resolution, though low plane‐to‐plane resolution. A stack of DTS slices can be reconstructed from a single limited‐angle scan, with typical scan angles ranging from 10° to 40° and acquisition times of less than . The resulting DTS slices show soft tissue contrast approaching that of full cone‐beam CT. External beam radiotherapy target localization using DTS requires the registration of on‐board DTS images with corresponding reference image data. This study evaluates three types of reference volume: original reference CT, exact reference DTS (RDTS), and a more computationally efficient approximate reference DTS , as well as three different DTS scan angles (22°, 44°, and 65°) for the DTS target localization task. Three‐dimensional mutual information (MI) shared between reference and on‐board DTS volumes was computed in a region surrounding the spine of a chest phantom, as translations spanning and rotations spanning were simulated along each dimension in the reference volumes. The locations of the MI maxima were used as surrogates for registration accuracy, and the width of the MI peaks were used to characterize the registration robustness. The results show that conventional treatment planning CT volumes are inadequate reference volumes for direct registration with on‐board DTS data. The efficient method also appears insufficient for MI‐based registration without further refinement of the technique, though it may be suitable for manual registration performed by a human observer. The exact RDTS volumes, on the other hand, delivered a 3D DTS localization accuracy of and 0.5° along each axis, using only a single 44° coronal on‐board DTS scan of the chest phantom.
Helical tomotherapy superficial dose measurements
Authors: Ramsey Chester R. , Seibert Rebecca M. , Robison Benjamin , Mitchell Martha
Published: August 2007

Helical tomotherapy is a treatment technique that is delivered from a fan beam that traces a helical path while the couch moves linearly into the bore. In order to increase the treatment delivery dose rate, helical tomotherapy systems do not have a flattening filter. As such, the dose distributions near the surface of the patient may be considerably different from other forms of intensity‐modulated delivery. The purpose of this study was to measure the dose distributions near the surface for helical tomotherapy plans with a varying separation between the target volume and the surface of an anthropomorphic phantom. A hypothetical planning target volume (PTV) was defined on an anthropomorphic head phantom to simulate a per fraction IMRT parotid‐sparing head and neck treatment of the upper neck nodes. A total of six target volumes were created with 0, 1, 2, 3, 4, and of separation between the surface of the phantom and the outer edge of the PTV. Superficial doses were measured for each of the treatment deliveries using film placed in the head phantom and thermoluminescent dosimeters (TLDs) placed on the phantom's surface underneath an immobilization mask. In the test case where the PTV extends to the phantom surface, the mean TLD dose was (or of the prescribed dose). The measured superficial dose decreases to ( of the prescribed dose) for a PTV‐surface separation of . The doses measured by the TLDs indicated that the tomotherapy treatment planning system overestimates superficial doses by . The radiographic film dose for the test case was , as compared to the calculated dose of . Given the results of the TLD and film measurements, the superficial calculated doses are overestimated between 3% and 13%. Without the use of bolus, tumor volumes that extend to the surface may be underdosed. As such, it is recommended that bolus be added for these clinical cases. For cases where the target volume is located below the surface, the tumor volume coverage can be achieved with surface doses ranging from 56% to 93% of the prescribed dose.
Functional imaging of cerebrovascular activities in small animals using high‐resolution photoacoustic tomography
Authors: Yang Sihua , Xing Da , Zhou Quan , Xiang Liangzhong , Lao Yeqi
Published: August 2007

Photoacoustic imaging (PAI) is a noninvasive, nonionizing modality based on the differences in light absorption of various biological tissues. PAI utilizes the endogenous contrast characteristics of traditional optical imaging, while benefiting from high spatial resolution of the ultrasound imaging. A PAI system was developed to reconstruct the two‐dimensional cross section image and to visualize the cerebrovascular activities of mouse in vivo. The spatial resolution of the PAI system was determined to be by a two‐point‐source phantom with the Rayleigh criterion. The potential applications of the system were clearly demonstrated by successfully mapping a traumatic lesion in the mouse brain cerebral cortex, by its ability to monitor physiological changes in the brain due to carotid ligation and drug stimulation, and two‐dimensional sliced images of a traumatic mouse brain at different depths were also provided. Our experimental results indicate that PAI has the potential for studying of traumatic brain injury and physiological functions of the brain.
UHRF1 Plays a Role in Maintaining DNA Methylation in Mammalian Cells
Authors: Bostick Magnolia , Kim Jong Kyong , Estève Pierre-Olivier , Clark Amander , Pradhan Sriharsa , Jacobsen Steven E.
Published: August 2007

Epigenetic inheritance in mammals relies in part on robust propagation of DNA methylation patterns throughout development. We show that the protein UHRF1 (ubiquitin-like, containing PHD and RING finger domains 1), also known as NP95 in mouse and ICBP90 in human, is required for maintaining DNA methylation. UHRF1 colocalizes with the maintenance DNA methyltransferase protein DNMT1 throughout S phase. UHRF1 appears to tether DNMT1 to chromatin through its direct interaction with DNMT1. Furthermore UHRF1 contains a methyl DNA binding domain, the SRA (SET and RING associated) domain, that shows strong preferential binding to hemimethylated CG sites, the physiological substrate for DNMT1. These data suggest that UHRF1 may help recruit DNMT1 to hemimethylated DNA to facilitate faithful maintenance of DNA methylation.
Exploring the Substrate Scope of the Ru(II)-Catalyzed Kharasch Reaction
Authors: Mume Eskender , Munslow Ian J. , Källström Klas , Andersson Pher G.
Published: August 2007

The Kharasch reaction, or atom-transfer addition of polyhalogenated alkanes to alkenes is known to be catalyzed by a number of Ru(II) complexes. The easily prepared [RuCl2(PPh3)3] was used to investigate the reaction scope. A number of halogenated alkanes were added to a range of alkenes with good to excellent regioselectivities.
Kinetics and Mechanism of Acid Catalysed Hydration of α-Methylstyrenes
Authors: Pytela Oldřich , Trlida Bronislav
Published: August 2007

Twelve para-substituted α-methylstyrenes with substituents H, CH3, CF3, CH3O, CH3S, F, Cl, Br, CH3CO, CH3SO2, CN a NO2 were synthesised; additionally, the acid catalysed hydration kinetics of these compounds were measured in sulfuric acid in a concentration range c from 0.017 to 9.58 mol l-1, at 25.0 °C. The observed rate constants obtained were used to construct the kinetic acidity function and calculate the catalytic rate constants. Based on the evaluation of the acidity function kinetic dependence on acid medium concentration, and the substituent effects of acid catalysed hydration of α-methylstyrenes on the catalytic rate constants, the mechanism of acid catalysed hydration was verified. The mechanism involves the addition of a proton to the double bond of α-methylstyrene in the rate-limiting reaction step denoted as A-SE2. No evident difference was found between the effects of the acid medium on the acid catalysed hydration of styrenes and α-methylstyrenes, which indicates very similar activity coefficients of the reactants, and of the transition state of both substrates. The substituent effects evaluation shows that the rate-limiting step of the reaction consists in the addition of a proton to the substrate. The carbocation formation in the transition state of this reaction step proceeds roughly half-way compared with the extent of the carbocation formation by cumyl chloride hydrolysis. The obtained carbocation is in particular stabilised by the substituents with +M effect, while the influence of the substituents with -M and I effects is significantly smaller.
Molecular changes in the progression of Barrett's oesophagus
Authors: Zagorowicz Edyta , Jankowski Janusz
Published: August 2007

Barrett's oesophagus is a frequent complication of gastro-oesophageal reflux disease predicting oesophageal adenocarcinoma. The majority of Barrett's patients will not develop cancer, so that specific methods of identification of those at risk are required. Recent molecular studies have identified a selection of candidate biomarkers that need validation in prospective studies. They reflect various changes in cell behaviour during neoplastic progression. The ASPECT trial in the UK aims to establish whether chemoprevention with aspirin and a proton pump inhibitor will reduce adenocarcinoma development and mortality in patients with Barrett's oesophagus. It will also validate biomarkers for progression and clinical response and further study disease pathogenesis.
Personal development plans and self-directed learning for healthcare professionals: are they evidence based?
Authors: Jennings Stephen F
Published: August 2007

The UK chief medical officer's recommendations for the re-licensing and performance management of doctors will mean a move from a formative towards a summative role for appraisal and its adjunct, the personal development plan. Where does this leave medical educators trying to promote reflective learning? It is taken for granted that self-directed learning is the sine qua non of all adult learning. But is it? This review re-evaluates self-directed learning and its corollary, the personal development plan, in the light of the chief medical officer's report, seeking the evidence behind today's accepted educational practice. It discovers a reality which challenges assumptions long enshrined in medical education.
Comparison of classical and non-classical cardiovascular risk factors influencing the patency of native arteriovenous fistulas after percutaneous transluminal angioplasty therapy among haemodialysis patients
Authors: Liu Jiung-Hsiun , Lin Po-Wen , Liu Yao-Lung , Lin Hsin-Hung , Huang Chiu-Ching
Published: August 2007

Objective

To evaluate the classical and non-classical cardiovascular risk factors that effect patency of native arteriovenous fistulas (AVF) in end stage renal disease (ESRD) patients who are undergoing regular haemodialysis treatment and have a percutaneous transluminal angioplasty (PTA) procedure.

Methods

All PTAs performed between 1 October 2002 and 30 September 2004 were identified from case notes and the computerised database and follow up to 31 March 2005. The definition of patency of AVF after PTA was including primary or secondary patencies. Risks were analysed to assess the influence on survival following PTAs of age, sex, serum cholesterol, serum triglyceride, diabetes, use of aspirin, current smoking and hypertension, serum albumin, serum calcium–phosphate product, intact parathyroid hormone (I-PTH), and urea reduction ratio (URR).

Results

The patency rate of AVFs of all interventions was 65% at 6 months. Factors with poor patencies of AVFs after PTA procedures were higher serum calcium–phosphate product (p = 0.033), higher URR (p<0.001), lower serum albumin (p<0.001), non-hypertension (p = 0.010) and “non-smoker + ex-smoker group” (p = 0.033). The hypertensive patients and current smokers had lower patency failure after PTAs (p<0.01 and p<0.05, respectively).

Conclusions

Unfavourable cumulative patency rates are observed in haemodialysis patients with higher URR, higher serum calcium–phosphate product and hypoalbuminaemia (lower serum albumin before the PTA procedure). Hypertension and current smoking were associated with better patency rates of AVF after PTA.
Community-acquired pneumonia: doctors do not follow national guidelines
Authors: Collini Paul , Beadsworth Mike , Anson Jim , Neal Tim , Burnham Peter , Deegan Paul , Beeching Nick , Miller Alastair
Published: August 2007

Objectives

Appropriate assessment of community-acquired pneumonia (CAP) allows accurate severity scoring and hence optimal management, leading to reduced morbidity and mortality. British Thoracic Society (BTS) guidelines provide an appropriate score. Adherence to BTS guidelines was assessed in our medical assessment unit (MAU) in 2001/2 and again in 2005/6, 3 years after introducing an educational programme.

Methods

A retrospective case-note study, comparing diagnosis, documentation of severity, management and outcome of CAP during admission to MAU during 3 months of each winter in 2001/2 and 2005/6.

Results

In 2001/2, 65/165 patients were wrongly coded as CAP and 100 were included in the study. In 2005/6 43/130 were excluded and 87 enrolled. In 2005/6, 87% did not receive a severity score, a significant increase from 48% in 2001/2 (p<0.0001). Parenteral antibiotics were given to 79% of patients in 2001/2 and 77% in 2005/6, and third generation cephalosporins were given to 63% in 2001/2 and 54% in 2005/6 (p = NS). In 2001, 15 different antibiotic regimens were prescribed, increasing to 19 in 2005/6.

Conclusions

Coding remains poor. Adherence to CAP management guidelines was poor and has significantly worsened. Educational programmes, alone, do not improve adherence. Restriction of antibiotic prescribing should be considered.
Bone hydatid disease
Authors: Song X H , Ding L W , Wen H
Published: August 2007

Bone hydatid disease lacks a typical clinical appearance and image characteristics on x ray or CT are similar to those of tuberculosis, metastases and giant cell tumour or bone cysts. However, MRI does show distinctive diagnostic features of bone hydatid disease, especially in the spine. Until recently, treatment of osseous hydatid disease has been entirely surgical. Effective chemotherapy using benzimidazoles, particularly mebendazole, albendazole and combination treatments, has now been achieved in experimental studies and clinical practice. However, most of these drugs are still in the experimental stage or are in the early stages of clinical use.
Kamdhenu Dairy
Authors: Pradhan Debasis , Kalra Shabad , Srinivas Sangeeta
Published: August 2007

Kamdhenu Dairy was one of the biggest dairy unions in India that came into being in 1969. Kamdhenu dairy, with an annual sales turnover of Rs.5250 million, was procuring its milk from the regular suppliers residing in the villages using its own procurement network. The same network was being used to market other dairy products and essential items like fodder and medicine for the cattle to the milk suppliers. The company had recently chosen to sell tea using the same procurement network. The entry of Kamdhenu Dairy into tea marketing was justified as tea was a high margin product and did not require additional resource allocation for marketing in the local rural market. As the marketing of Kamdhenu Dan (cattle feed) and Kamdhenu Ghee had been quite successful, Mr. Samal, the CEO of Kamdhenu, thought the same network could be used to market Kamdhenu tea as well.

However, Mr. Samal was worried over the stagnation of tea sales in recent times though initial sales were encouraging. There were already many national and local players who were quite entrenched in the regional tea markets of India. Kamdhenu dairy was neither a national player nor was it a leader in the local market. This forced Mr. Samal to think about the marketing strategy for Kamdhenu tea to achieve success in market penetration in India. Mr. Samal was carefully pondering over possible alternatives to decide how best he can deal with the situation. This case is useful for examining the issues related to market penetration strategy.
DENA BANK — Competing with Private and Foreign Banks
Authors: Sachan Amit , Ali Anwar , Gupta Rajen K.
Published: August 2007

Since 1995 with the increasing importance of the service sector, liberalization policy and information technology revolution, the banking sector as a whole had undergone significant changes in India. The case presents a brief outline of the developments which happened in the Indian banking sector and discusses Dena Bank's efforts in the last decade in the area of customer service. The case explores how customers interacted with banks, how banks made money, how external environment was changing the core activities and core assets of banks in India and the opportunities and challenges arising out of all these. The case ends with the question on what Dena's strategy should be in response to the new competition and new technologies. The case is useful in looking at strategic responses to changes.
REQUIREMENTS FOR AN EVENT-BASED SIMULATION PACKAGE FOR GRID SYSTEMS
Authors: XHAFA FATOS , CARRETERO JAVIER , BAROLLI LEONARD , DURRESI ARJAN
Published: August 2007

In this paper we present a study on the requirements for the design and implementation of simulation packages for Grid systems. Grids are emerging as new distributed computing systems whose main objective is to manage and allocate geographically distributed computing resources to applications and users in an efficient and transparent manner. Grid systems are at present very difficult and complex to use for experimental studies of large-scale distributed applications. Although the field of simulation of distributed computing systems is mature, recent developments in large-scale distributed systems are raising needs not present in the simulation of the traditional distributed systems. Motivated by this, we present in this work a set of basic requirements that any simulation package for Grid computing should offer. This set of functionalities is obtained after a careful review of most important existing Grid simulation packages and includes new requirements not considered in such simulation packages. Based on the identified set of requirements, a Grid simulator is developed and exemplified for the Grid scheduling problem.
CAPTURING AND RE-USING ARTISTIC STYLES WITH REVERSE SUBDIVISION-BASED MULTIRESOLUTION METHODS
Authors: BRUNN MERU , SOUSA MARIO COSTA , SAMAVATI FARAMARZ F.
Published: August 2007

We describe a multiresolution method for rendering curves that is based on exact reproduction of artistic silhouettes and line hand-gesture styles. Using analysis based on reverse subdivision, we extract examples from both scanned images of line-drawn artwork and interactively-sketched input and apply these styles to the arbitrary strokes of new illustrations. Our algorithms work directly with the extracted discrete point data using fast and simple local and global multiresolution filters, and we support the use of styles with gaps or discontinuities. Our results show how this technique can capture the complex contour drawings of landscape elements, allowing users without drawing skills to easily reproduce them.
ADDRESSING THE PROBLEMS OF DETECTING FACES WITH NEURAL NETWORKS
Authors: CURRAN KEVIN , McCAUGHLEY NEIL , LI XUELONG
Published: August 2007

The face is the most distinctive and widely used key to a person's identity. The area of face detection has attracted considerable attention in the advancement of human-machine interaction as it provides a natural and efficient way to communicate between humans and machines. The problem of facial parts in image sequences has become a popular area of research due to emerging applications in intelligent human-computer interface, surveillance systems, content-based image retrieval, video conferencing, financial transaction, forensic applications, pedestrian detection, image database management system and so on. This paper presents the results of an image based neural network face detection system which seeks to address the problem of detecting faces under gross variations.
FUSION OF THE MAGNETIC AND OPTICAL INFORMATION FOR MOTION CAPTURING
Authors: PARK CHAN JONG , WOHN KWANG YUN
Published: August 2007

We propose a sensor fusion technique for motion capture system. In our system, two kinds of sensors are used for mutual assistance. Six magnetic sensors are attached on the arms and feet for assisting twelve optical markers and six optical markers, which are attached on the arms and feet of a performer, respectively. The optical marker information is not always complete because the optical markers can be hidden due to obstacles. In this case, magnetic sensor information is used to link discontinuous optical marker information. We use a system identification technique for modeling the relation between the two signals of sensor and marker. We determine the best model from the set of candidate models using the canonical system identification technique. In order to show the efficiency of the proposed system, experiments are performed for motion capture data obtained from both the optical and magnetic motion capture system, and the animation results are shown.
DAUBECHIES COMPLEX WAVELET TRANSFORM BASED TECHNIQUE FOR DENOISING OF MEDICAL IMAGES
Authors: KHARE ASHISH , TIWARY UMA SHANKER
Published: August 2007

Wavelet based denoising is an effective way to improve the quality of images. Various methods have been proposed for denoising using real-valued wavelet transform. Complex valued wavelets exist but are rarely used. The complex wavelet transform provides phase information and it is shift invariant in nature. In medical image denoising, both removal of phase incoherency as well as maintaining the phase coherency are needed. This paper is an attempt to explore and apply the complex Daubechies wavelet transform for medical image denoising.

We have proposed a method to compute a complex threshold, which does not depend on any assumed model of noise. In this sense this is a "universal" method. The proposed complex-domain shrinkage function depends on mean, variance and median of wavelet coefficients. To test the effectiveness of the proposed method, we have computed the input and output SNR and PSNR of various types of medical images. The method gives an improvement for Gaussian additive, Speckle and Salt-&-Pepper noise as well as for the mixture of these noise types for a range of noisy images with 15 db to 30 db noise levels and outperforms other real-valued wavelet transform based methods. The application of the proposed method to Ultrasound, X-ray and MRI images is demonstrated in the experiments.
COMPREHENSIVE 3D FIBER TRACKING AS A NEW VISUALIZATION SYSTEM IN BRAIN STUDIES
Authors: SANCHEZ DANMARY , ADJOUADI MALEK , ALTMAN NOLAN R. , SANCHEZ DANIEL , BERNAL BYRON
Published: August 2007

Comprehensive spatial visualization of fiber tracts from all perspectives is a highly desirable outcome in brain studies. To achieve this aim, this study establishes the foundation for a new 3D visual interface that integrates Magnetic Resonance Imaging (MRI) to Diffusion Tensor Imaging (DTI). The need for such an interface is critical for understanding brain dynamics, and for providing accurate diagnosis of key brain dysfunctions, in terms of neuronal connectivity in the human brain. Two research fronts were explored: (1) the development of new image processing techniques resulting in comprehensive visualization mechanisms that accurately establish relational positioning of neuronal fiber tracts and key landmarks in semi-transparent 3D brain images, and (2) the design of key algorithms that do not tax the computational requirements of 3D rendering and feature extraction using 2D MRI and DTI frames, remaining within practical time constraints. The system was evaluated using data from thirty patients and volunteers with the Brain Institute at Miami Children's Hospital. The highly integrated and fully embedded fiber-tracking software system provides an optimal research environment for innovative visualization mechanisms of white matter fiber tracts. This 3D visualization system reached the implementation level that makes it ready for deployment at other clinical sites.
A HIGHER ORDER FINITE ELEMENT MODELING OF PIEZOLAMINATED SMART COMPOSITE PLATES AND ITS APPLICATION TO ACTIVE VIBRATION CONTROL
Authors: BALAMURUGAN V. , MANIKANDAN B. , NARAYANAN S.
Published: August 2007

This paper presents a higher order — field consistent — piezolaminated 8-noded plate finite element with 36 elastic degrees-of-freedom per element and two electric degrees-of-freedom per element, one each for the piezoelectric sensor and actuator. The higher order plate theory used satisfies the stress and displacement continuity at the interface of the composite laminates and has zero shear stress on the top and bottom surfaces. The transverse shear deformation is of a higher order represented by the trigonometric functions allowing us to avoid the shear correction factors. In order to maintain the field consistency, the inplane displacements, u and v are interpolated using linear shape functions, the transverse displacement w is interpolated using hermite cubic interpolation function, while rotations θx and θy are interpolated using quadratic interpolation function. The element is developed to include stiffness and the electromechanical coupling of the piezoelectric sensor/actuator layers. The active vibration control performance of the piezolaminated smart composite plates has been studied by modeling them with the above element and applying various control strategies.
Terranes
Authors: Bluck B. J. , Gibbons W. , Ingham J. K.
Published: August 2007

The Precambrian and Lower Palaeozoic foundations of the British Isles may be viewed as a series of suspect terranes whose exposed boundaries are prominent fault systems of various kinds, each with an unproven amount of displacement. There are indications that they accreted to their present configuration between late Precambrian and Carboniferous times. From north to south they are as follows.

In northwest Scotland the Hebridean terrane (Laurentian craton in the foreland of the Caledonian Orogen) comprises an Archaean and Lower Proterozoic gneissose basement (Lewisian) overlain by an undeformed cover of Upper Proterozoic red beds and Cambrian to early mid Ordovician shallow marine sediments. The terrane is cut by the Outer Isles Thrust, a rejuvenated Proterozoic structure, and is bounded to the southeast by the Moine Thrust zone, within the hanging wall of which lies a Proterozoic metamorphic complex (Moine Supergroup) which constitutes the Northern Highlands terrane. The Moine Thrust zone represents an essentially orthogonal closure of perhaps 100 km which took place during Ordovician-Silurian times (Elliott & Johnson 1980). The Northern Highlands terrane records both Precambrian and late Ordovician to Silurian tectonometamorphic events (Dewey & Pankhurst 1970) and linkage with the Hebridean terrane is provided by slices of reworked Lewisian basement within the Moine Supergroup (Watson 1983).

To the southwest of the Great Glen-Walls Boundary Fault system lies the Central Highlands (Grampian) terrane, an area dominated by the late Proterozoic Dalradian Supergroup which is underlain by a gneissic complex (Central Highland Granulites) that has been variously interpreted as either older
Triassic
Authors: Warrington G. , Ivimey-Cook H. C.
Published: August 2007

"The Triassic rocks of Great Britain, if one may judge from statements in the textbooks, are among the simplest of our deposits; but a closer inspection reveals a number of very difficult and intensely interesting problems hidden behind this apparent simplicity." L. J. Wills, 1910.

During latest Permian times, northerly-sourced epeiric marine environments, in which the Zechstein sequence formed, were replaced by predominantly clastic sedimentary regimes. The succeeding Triassic deposits, representing about 45 million years, are largely continental; some formed under transient marine influences but few are biogenic. They succeed Permian deposits conformably and overstep these to rest unconformably upon older rocks. Over much of the region the youngest Triassic deposits represent a transgression that re-established marine environments before the end of the Period.

The region lay in Laurasia, the northern part of the Pangaean supercontinent, some 15 to 20° north of the equator and close to the northern margin of the Tethys (Tollmann & Kristan-Tollmann 1985) but separated from that ocean by the Variscan mountain chain, denudation of which continued from Permian into Triassic times. A monsoonal climate is envisaged (Robinson 1973; Parrish & Curtis 1982; Parrish
et al
. 1982).

The principal onshore Triassic occurrences are in England and Northern Ireland; others in the British Isles are relatively minor (Warrington
et al
. 1980, figs 2 & 3). Concealed developments in The Netherlands (Map Tr2) and northeast France (Mégnien & Mégnien 1980; Debrand-Passard 1980; Berners
et al
. 1984; Maps Tr2-3b & 4c) are contiguous with the tripartite German sequence from
Jurassic
Authors: Bradshaw M. J. , Cope J. C. W. , Cripps D. W. , Donovan D. T. , Howarth M. K. , Rawson P. F. , West I. M. , Wimbledon W. A.
Published: August 2007

The interplay of regional or global sea-level changes and continuing crustal extension related to rifting in the North Atlantic and Tethyan megarifts dominated the palaeogeographical evolution of the area. The sea-level rise that commenced in the Rhaetian continued into the Jurassic to usher in a new phase of predominantly marine sedimentation across northwest Europe. The climate was warm and humid, the seas generally shallow. Land areas became well vegetated, as attested by the abundance of fossil driftwood in marine as well as non-marine sediments. The region probably lay about 10° south of present latitudes, in an area of overlap of Tethyan and Boreal marine realms. For much of the Jurassic, sea levels continued to rise but two major falls occurred, coinciding with accelerated extensional movements in the area. The first was during the mid-Jurassic ('mid-Cimmerian phase') when there was a major regional upwarp centred on the North Sea, and the second across the Jurassic/Cretaceous boundary ('late Cimmerian phase') when a global fall in sea level coincided with an important phase of rifting and block faulting. Major structural trends generally follow previously established lines. The basic structural framework for the Jurassic maps has been compiled from numerous sources, including Andrews &Brown (1987); Dunning (1985); Evans et al. (1982); Gardiner &Sheridan (1981); Van Hoorn (1987); Thomas et al. (1985); Whittaker (1985); Ziegler (1982, 1987); and papers in Brooks &Glennie (1987). Fault trends are generalized and selected to pick out the main structural features controlling the geography; their occurrence on
Carboniferous
Authors: Cope J. C. W. , Guion P. D. , Sevastopulo G. D. , Swan A. R. H.
Published: August 2007

Carboniferous geology has developed very rapidly over the past two decades since ideas on sedimentology and new radiometric scales, together with new biostratigraphical schemes based on miospores, conodonts and foraminifera have been synthesized with ideas on plate tectonic processes, climatic changes and oscillations of sea level. The application of the McKenzie model of basin development to the Carboniferous, and the relating of eustatic sea-level changes, which had a profound effect on Carboniferous palaeo-geography, to fluctuations in the size of the Gondwanan ice sheets, have been major factors in the understanding of Carboniferous processes. The Carboniferous evolution of Britain took place to the (present) north of a plate suturing occurring along a line extending from Galicia, through Armorica and the Massif Central to the Vosges, during mid Devonian to early Carboniferous times. In front of this collision zone was the Rheno-Hercynian zone which opened probably during mid Devonian times and which was partly floored by oceanic crust; its closure can be traced through to late Carboniferous times as a series of northwardly directed thrust complexes. To the (present) north of this zone was a foreland on which basins developed on either side of a persistent Wales-London-Brabant High. Studies by Dewey (1982) and Leeder (1982, 1987, 1988) have shown that late Devonian to early Carboniferous extension, involving β factors of up to 2, produced a series of grabens and half-grabens in the Caledonian basement. These developing structures were the dominant control on early Carboniferous sedimentation and produced a sea-bed topography which was
Part 1: Compendium of North Sea Oil and gas fields
Authors: Warren E. A. , Smalley P. C.
Published: August 2007

This section gives an alphabetical field-by-field compilations of water compositions with accompanying geological descriptions and field maps.

The following abbreviations are used:

AA -- atomic absorption (spectroscopy)

API -- American Petroleum Institute

BCF -- billion cubic feet

DST -- drill stem test

KCF -- Kimmeridge Clay Formation

ICP-AES -- inductively coupled plasma - atomic emission spectroscopy

MMbbls -- million barrels

psi -- pounds per square inch

Prod -- production (sample)

RFT -- repeat formation tester

SMOW -- standard mean ocean water

stb/d -- stock tank barrels per day

TDS -- total dissolved solids

TVD -- true vertical depth

TU -- tritium unit

UKCS -- United Kingdom continental shelf
Part 2: SPWLA Water Resistivity (R
w
) Atlas
Authors: Warren E. A. , Smalley P. C.
Published: August 2007

The resistivity (R
w
) of formation waters is directly related to salinity: the higher the salinity the lower the water resistivity. Knowledge of formation water resistivity is essential in formation evaluation. Most importantly, it is used to derive estimates of water saturation in the hydrocarbon column and, hence, of the volumes of petroleum initially in place.

The resistivity of formation waters is determined by direct electrical measurement in a resistivity cell or estimated, either from chemical analysis or from electric logs. An atlas of formation water resistivity for the North Sea was published by the Society of Professional Well Log Analysts (SPWLA) in 1989 (Amiard & Harrison 1989). The data compiled for this volume were used to update the SPWLA atlas. These new data are presented together with the earlier 1989 data in the same format used by the SPWLA.

Tables and maps of formation water resistivity have been produced according to the guidelines of Amiard & Harrison (1989). These are described below.

A salt-saturated brine at 60°F (15.6°C) and at atmospheric pressure has a maximum salinity of approximately 250 000 ppm NaCl equivalent and is represented as a minimum normalized R
w
value of 0.050 Ω m.

All R
w
data are reported for a standard temperature of 60°F (15.6°C). Corrections to the resistivity value from the actual measurement temperature to this standard temperature were made using the formulae:

In keeping with Amiard & Harrison (1989), a validity index was assigned to the data. This index attempts subjectively to rank the data
Setting, chronology and consequences of the eruption of Soufrière Hills Volcano, Montserrat (1995-1999)
Authors: Kokelaar B. P.
Published: August 2007

The eruption on Montserrat during 1995-1999 was the most destructive in the Caribbean volcanic arc since that of Mont Pelee (Martinique) in 1902. It began on 18 July 1995 at the site of the most recent previous activity, on the flank of a c. 350-year-old lava dome within a sector-collapse scar. Phreatic explosivity occurred for 18 weeks before the onset of extrusion of an andesitic lava dome. Dome collapses produced pyroclastic flows that initially were confined by the sector-collapse scar. After 60 weeks of unsteadily accelerating dome growth and one episode of sub-Plinian explosivity, the dome eventually overtopped the confining scar. During 1997 almost two-thirds of the island was devastated following major dome collapses, two episodes of Vulcanian explosivity with fountain-collapse pyroclastic flows, and a flank failure with associated debris avalanche and explosive disruption of the lava dome. Nineteen people were killed directly by the volcanic activity and several were injured. From March 1998 until November 1999 there was a pause in magma ascent accompanied by reduced seismic activity, substantial degradation of the dome, and considerable degassing with venting of ash.

The slow progress and long duration of the volcanic escalation, coupled with the small size of the island and the vulnerability of homes, key installations and infrastructure, resulted in a style of emergency management that was dominantly reactive. In order to minimize the disruption to life for those remaining on the island, following large-scale evacuations, scientists at the Montserrat Volcano Observatory had to anticipate hazards and their potential extents of impact with considerable precision. Based on frequent hazards assessments, a series of risk management zone maps was issued by administrative authorities to control access as the eruption escalated. These were used in conjunction with an alert-level system. The unpreparedness of the Montserrat authorities and the responsible UK government departments resulted in hardship, ill feeling and at times acrimony as the situation deteriorated and needs for aid mounted. Losses and stress could have been less if an existing hazards assessment had registered with appropriate authorities before the eruption.
The volcanic evolution of Montserrat using
40
Ar/
39
Ar geochronology
Authors: Harford C. L. , Pringle M. S. , Sparks R. S. J. , Young S. R.
Published: August 2007

40
Ar/
39
Ar dating has facilitated a substantial reinterpretation of the volcanic evolution of Montserrat. Three volcanic centres with non-overlapping volcanic activity are identified: Silver Hills (c. 2600 to c. 1200 ka); Centre Hills (at least c. 950 to c. 550 ka); South Soufrière Hills-Soufrière Hills (at least c. 170 ka to present). The geochronological data show that old xenocrysts are common in the porphyritic andesite, implying that reliable ages are best obtained by dating the groundmass. Soufrière Hills evolved from early eruptions dominated by two-pyroxene andesite to eruptions of hypersthene-hornblende andesite at c. llOka. Between the two varieties of andesite there was an interlude of mafic volcanism at c. 130ka to form South Soufrière Hills. There is evidence of tectonic uplift of early products of the complex along with older submarine volcanic rocks. Consideration of stratigraphy and age data indicates that only a proportion of the dome-forming eruptions are recorded as domes in the geological record. Older products are removed from the subaerial edifice by sector-collapse events. The time-averaged eruption rate of the South Soufrière Hills-Soufrière Hills centre is estimated at 0.005 m
3
s
-1
(c. 0.15 km
3
ka
-1
) (dense rock equivalent). The ongoing eruption is very similar in style to previous activity at Soufrière Hills, and future activity is likely to pose similar hazards. Soufrière Hills have been characterized by alternations of periods of enhanced activity and periods of dormancy, both lasting of the order of 10
4
years. During periods of elevated activity several major dome-forming eruptions are separated by quiescent interludes lasting less than c. 10
3
years. The ongoing eruption may mark the onset of a fourth period of enhanced volcanic activity at Soufrière Hills.
Deposits from dome-collapse and fountain-collapse pyroclastic flows at Soufrière Hills Volcano, Montserrat
Authors: Cole P. D. , Calder E. S. , Sparks R. S. J. , Clarke A. B. , Druitt T. H. , Young S. R. , Herd R. A. , Harford C. L. , Norton G. E.
Published: August 2007

abstract

Pyroclastic flows were formed at Soufrière Hills Volcano by lava-dome collapse and by fountain collapse associated with Vulcanian explosions. Major episodes of dome collapse, lasting tens of minutes to a few hours, followed escalating patterns of progressively larger flows with longer runouts. Block-and-ash flow deposit volumes range from <0.1 to 25 x 10
6
m
3
with runouts of 1-7 km. The flows formed coarse-grained block-and-ash flow deposits, with associated fine-grained pyroclastic surge deposits and ashfall deposits. Small flows commonly formed lobate channelized deposits. Large block-and-ash flows in unconfined areas produced sheet-like deposits with tapering margins. the development of pyroclastic surges was variable depending on topography and dome pore pressure. Pyroclastic surge deposits commonly had a lower layer poor in fine ash that was formed at the current front and an upper layer rich in fine ash. Block-and-ash flows were erosive, producing striated and scoured bedrock surfaces and forming channels, many metres deep, in earlier deposits. Abundant accidental material was incorporated. Pyroclastic flow deposits formed by fountain collapse were pumiceous, with narrow sinuous, lobate morphologies and well developed levees and snouts. Two coastal fans formed where pyroclastic flows entered the sea. Their seaward extent was limited by a submarine slope break.
The 26 December (Boxing Day) 1997 sector collapse and debris avalanche at Soufrière Hills Volcano, Montserrat
Authors: Voight B. , Komorowski J-C. , Norton G. E. , Belousov A. B. , Belousova M. , Boudon G. , Francis P. W. , Franz W. , Heinrich P. , Sparks R. S. J. , Young S. R.
Published: August 2007

The southern sector of Soufrière Hills Volcano failed on 26 December 1997 (Boxing Day), after a year of disturbance culminating in a devastating eruptive episode. Sector collapse produced a
c.
50 x 10
6
m
3
volcanic debris avalanche, and depressurized the interior of the lava dome, which exploded to generate a violent pyroclastic density current. The south-directed growth of a lava lobe and build-up of lava-block talus, since early November 1997, brought the hydrothermally weakened sector to a condition of marginal stability. Limit-equilibrium stability analyses and finite-difference stress-deformation analyses, constrained by geomechanical testing of edifice and debris avalanche materials, suggest that the sector collapse was triggered by a pulse of co-seismic exogenous lava shear-lobe emplacement. Slip-surface localization was influenced by strain-weakening.

The source region fragmented into avalanche megablocks, and further disruption generated a chaotic avalanche mixture that included variably indurated and coloured hydrothermally altered material, and much talus. The avalanche consisted of several flow pulses that reflected complexities of source disruption and channel topography. In the proximal zone, within 1.5 km from source, many megablocks preserve pre-collapse stratigraphy. At major bends the avalanche separated into channelled and overspill flows. In the distal region, <2.5km from source, stacked sets of the main lithologies occur with a hummocky surface and abrupt flowage snouts, beyond which sparse hummocks occur in a thinly spread deposit. Textures suggest emplacement by laminar mass transport of partly saturated debris riding on a frictionally sheared base. Three-dimensional numerical simulations of emplacement governed by a Coulomb-type (Pouliquen) basal friction law imply low values of friction (> 15°), consistent with geotechnical test data and the localized presence of pore-water pressures. The best-fit model suggests an emplacement time >3 minutes and a typical maximum velocity of about 40ms
_1
, which are consistent with field estimates.
The explosive decompression of a pressurized volcanic dome: the 26 December 1997 collapse and explosion of Soufrière Hills Volcano, Montserrat
Authors: Woods A. W. , Sparks R. S. J. , Ritchie L. J. , Batey J. , Gladstone C. , Bursik M. I.
Published: August 2007

Abstract: We calculate the gas flux through a pressurized and permeable lava dome as magma slowly ascends to the surface and degasses. This provides an estimate of the mass of gas and the associated energy that may be released following the explosive collapse of such a dome. We estimate that during the 26 December 1997 dome failure of Soufrière Hills Volcano, up to 10
16
J of energy was released. We then develop a model of the dome break-up driven by the pressure jump across a fragmentation wave. We predict that the fragmentation front advances into the dome at a speed of order 10 ms
-1
, while the gas and solid fragments issue from the dome at speeds of order 50-60 ms
-1
. This fragmented material forms a dense fountain of gas and solid fragments. This may rise 100-200 m above the dome and then spread out to form a dense pyroclastic density current, with initial density of order a few hundred kilograms per cubic metre. We anticipate that such flows will become stratified in density and mean grain size. Some new experiments on stratified gravity currents illustrate that the flow propagation speed is similar to a well mixed current of the same total buoyancy, although the flow tends to become laterally stratified, with the dense lower region out-running the fluid higher in the current.