bluuebunny/crossref_metadata_2025 huggingface dataset:
Feature‐based characterization of motion‐contaminated calcified plaques in cardiac multidetector CT
Authors: King Martin , Giger Maryellen L. , Suzuki Kenji , Pan Xiaochuan
Published: December 2007

In coronary calcium scoring, motion artifacts affecting calcified plaques are commonly characterized using descriptive terms, which incorporate an element of subjectivity in their interpretations. Quantitative indices may improve the objective characterization of these motion artifacts. In this paper, an automated method for generating 12 quantitative indices, i.e., features that characterize the motion artifacts affecting calcified plaques, is presented. This method consists of using the rapid phase‐correlated region‐of‐interest (ROI) tracking algorithm for reconstructing ROI images of calcified plaques automatically from the projection data obtained during a cardiac scan, and applying methods for extracting features from these images. The 12 features include two dynamic, six morphological, and four intensity‐based features. The two dynamic features are three‐dimensional (3D) velocity and 3D acceleration. The six morphological features include edge‐based volume, threshold‐based volume, sphericity, irregularity, average margin gradient, and variance of margin gradient. The four intensity‐based features are maximum intensity, mean intensity, minimum intensity, and standard deviation of intensity. The 12 features were extracted from 54 reconstructed sets of simulated four‐dimensional images from the dynamic NCAT phantom involving six calcified plaques under nine heart rate/multi‐sector gating combinations. In order to determine how well the 12 features correlated with a plaque motion index, which was derived from the trajectory of the plaque, partial correlation coefficients adjusted for heart rate, number of gated sectors, and mean feature values of the six plaques were calculated for all 12 features. Features exhibiting stronger correlations with the motion index were 3D velocity, maximum intensity, and standard deviation of intensity. Features demonstrating stronger correlations with other features mostly involved intensity‐based features. Edge‐based volume/irregularity and average margin gradient/variance of margin gradient were the only two feature pairs out of 12 with stronger correlations that did not involve intensity‐based features. Automatically extracted features of the motion artifacts affecting calcified plaques in cardiac computed tomography images potentially can be used to develop models for predicting image assessability with respect to motion artifacts.
Design and dosimetry of a few leaf electron collimator for energy modulated electron therapy
Authors: Al‐Yahya Khalid , Verhaegen Frank , Seuntjens Jan
Published: December 2007

Despite the capability of energy modulated electron therapy (EMET) to achieve highly conformal dose distributions in superficial targets it has not been widely implemented due to problems inherent in electron beam radiotherapy such as planning dosimetry accuracy, and verification as well as a lack of systems for automated delivery. In previous work we proposed a novel technique to deliver EMET using an automated “few leaf electron collimator” (FLEC) that consists of four motor‐driven leaves fit in a standard clinical electron beam applicator. Integrated with a Monte Carlo based optimization algorithm that utilizes patient‐specific dose kernels, a treatment delivery was incorporated within the linear accelerator operation. The FLEC was envisioned to work as an accessory tool added to the clinical accelerator. In this article the design and construction of the FLEC prototype that match our compact design goals are presented. It is controlled using an in‐house developed EMET controller. The structure of the software and the hardware characteristics of the EMET controller are demonstrated. Using a parallel plate ionization chamber, output measurements were obtained to validate the Monte Carlo calculations for a range of fields with different energies and sizes. Further verifications were also performed for comparing 1‐D and 2‐D dose distributions using energy independent radiochromic films. Comparisons between Monte Carlo calculations and measurements of complex intensity map deliveries show an overall agreement to within . This work confirms our design objectives of the FLEC that allow for automated delivery of EMET. Furthermore, the Monte Carlo dose calculation engine required for EMET planning was validated. The result supports the potential of the prototype FLEC for the planning and delivery of EMET.
Thermal neutron irradiation field design for boron neutron capture therapy of human explanted liver
Authors: Bortolussi S. , Altieri S.
Published: December 2007

The selective uptake of boron by tumors compared to that by healthy tissue makes boron neutron capture therapy (BNCT) an extremely advantageous technique for the treatment of tumors that affect a whole vital organ. An example is represented by colon adenocarcinoma metastases invading the liver, often resulting in a fatal outcome, even if surgical resection of the primary tumor is successful. BNCT can be performed by irradiating the explanted organ in a suitable neutron field. In the thermal column of the Triga Mark II reactor at Pavia University, a facility was created for this purpose and used for the irradiation of explanted human livers. The neutron field distribution inside the organ was studied both experimentally and by means of the Monte Carlo ‐particle transport code (MCNP). The liver was modeled as a spherical segment in MCNP and a hepatic‐equivalent solution was used as an experimental phantom. In the as‐built facility, the ratio between maximum and minimum flux values inside the phantom was 3.8; this value can be lowered to 2.3 by rotating the liver during the irradiation. In this study, the authors proposed a new facility configuration to achieve a uniform thermal neutron flux distribution in the liver. They showed that a ratio of 1.4 could be obtained without the need for organ rotation. Flux distributions and dose volume histograms were reported for different graphite configurations.
Report of the AAPM Task Group No. 105: Issues associated with clinical implementation of Monte Carlo‐based photon and electron external beam treatment planning
Authors: Chetty Indrin J. , Curran Bruce , Cygler Joanna E. , DeMarco John J. , Ezzell Gary , Faddegon Bruce A. , Kawrakow Iwan , Keall Paul J. , Liu Helen , Ma C.‐M. Charlie , Rogers D. W. O. , Seuntjens Jan , Sheikh‐Bagheri Daryoush , Siebers Jeffrey V.
Published: December 2007

The Monte Carlo (MC) method has been shown through many research studies to calculate accurate dose distributions for clinical radiotherapy, particularly in heterogeneous patient tissues where the effects of electron transport cannot be accurately handled with conventional, deterministic dose algorithms. Despite its proven accuracy and the potential for improved dose distributions to influence treatment outcomes, the long calculation times previously associated with MC simulation rendered this method impractical for routine clinical treatment planning. However, the development of faster codes optimized for radiotherapy calculations and improvements in computer processor technology have substantially reduced calculation times to, in some instances, within minutes on a single processor. These advances have motivated several major treatment planning system vendors to embark upon the path of MC techniques. Several commercial vendors have already released or are currently in the process of releasing MC algorithms for photon and/or electron beam treatment planning. Consequently, the accessibility and use of MC treatment planning algorithms may well become widespread in the radiotherapy community. With MC simulation, dose is computed stochastically using first principles; this method is therefore quite different from conventional dose algorithms. Issues such as statistical uncertainties, the use of variance reduction techniques, theability to account for geometric details in the accelerator treatment head simulation, and other features, are all unique components of a MC treatment planning algorithm. Successful implementation by the clinical physicist of such a system will require an understanding of the basic principles of MC techniques. The purpose of this report, while providing education and review on the use of MC simulation in radiotherapy planning, is to set out, for both users and developers, the salient issues associated with clinical implementation and experimental verification of MC dose algorithms. As the MC method is an emerging technology, this report is not meant to be prescriptive. Rather, it is intended as a preliminary report to review the tenets of the MC method and to provide the framework upon which to build a comprehensive program for commissioning and routine quality assurance of MC‐based treatment planning systems.
Optical Quantum Computing
Authors: O'Brien Jeremy L.
Published: December 2007

In 2001, all-optical quantum computing became feasible with the discovery that scalable quantum computing is possible using only single-photon sources, linear optical elements, and single-photon detectors. Although it was in principle scalable, the massive resource overhead made the scheme practically daunting. However, several simplifications were followed by proof-of-principle demonstrations, and recent approaches based on cluster states or error encoding have dramatically reduced this worrying resource overhead, making an all-optical architecture a serious contender for the ultimate goal of a large-scale quantum computer. Key challenges will be the realization of high-efficiency sources of indistinguishable single photons, low-loss, scalable optical circuits, high-efficiency single-photon detectors, and low-loss interfacing of these components.
Economics of Overexploitation Revisited
Authors: Grafton R. Q. , Kompas T. , Hilborn R. W.
Published: December 2007

About 25% of the world's fisheries are depleted such that their current biomass is lower than the level that would maximize the sustained yield (MSY). By using methods not previously applied in the fisheries conservation context, we show in four disparate fisheries (including the long-lived and slow-growing orange roughy) that the dynamic maximum economic yield (MEY), the biomass that produces the largest discounted economic profits from fishing, exceeds MSY. Thus, although it is theoretically possible that maximizing discounted economic profits may cause stock depletions, our results show there is a win-win: In many fisheries at reasonable discount rates and at current prices and costs, larger fish stocks increase economic profits. An MEY target that exceeds MSY and transfers from higher, future profits to compensate fishers for the transition costs of stock rebuilding would help overcome a key cause of fisheries overexploitation, industry opposition to lower harvests.
Evaluation of the Ultrasensitive Human Immunodeficiency Virus Type 1 (HIV-1) p24 Antigen Assay Performed on Dried Blood Spots for Diagnosis of HIV-1 Infection in Infants
Authors: Patton Janet C. , Coovadia Ashraf H. , Meyers Tammy M. , Sherman Gayle G.
Published: December 2007

The diagnostic accuracy of the modified p24 antigen assay performed on pediatric dried blood spots was evaluated. Samples analyzed within 6 weeks of collection yielded no false-positive results (specificity, 100%) and few false-negative results (sensitivity, 96.5% to 98.3%). Laboratory services with limited resources should assess this option for routine infant diagnosis.
Induction of Antitumor Acquired Immunity by Baculovirus
Autographa californica
Multiple Nuclear Polyhedrosis Virus Infection in Mice
Authors: Kitajima Masayuki , Takaku Hiroshi
Published: December 2007

The baculovirus
Autographa californica
multiple nuclear polyhedrosis virus (AcMNPV) has been studied as a gene therapy vector. Here, we demonstrated that AcMNPV induces antitumor acquired immunity. These results suggest that AcMNPV has the potential to be an efficient virus or tumor therapy agent which induces innate and acquired immunity.
Evaluation of the One-Step Multiplex Real-Time Reverse Transcription-PCR ProFlu-1 Assay for Detection of Influenza A and Influenza B Viruses and Respiratory Syncytial Viruses in Children
Authors: LeGoff Jérôme , Kara Rachid , Moulin Florence , Si-Mohamed Ali , Krivine Anne , Bélec Laurent , Lebon Pierre
Published: December 2007

We evaluated the one-step multiplex real-time reverse transcription-PCR ProFlu-1 assay for the detection of influenza A and influenza B viruses and respiratory syncytial viruses from 353 pediatric nasopharyngeal aspirates. As assessed by comparison with the results of immunofluorescence testing and cell culture, the specificity and the sensitivity of the ProFlu-1 assay ranged from 97% to 100%. In addition, the ProFlu-1 assay amplified 9% of samples not detected by conventional methods.
Prediction of Cytomegalovirus (CMV) Plasma Load from Evaluation of CMV Whole-Blood Load in Samples from Renal Transplant Recipients
Authors: Garrigue Isabelle , Doussau Adélaïde , Asselineau Julien , Bricout Hélène , Couzi Lionel , Rio Catherine , Merville Pierre , Fleury Hervé , Lafon Marie-Edith , Thiébaut Rodolphe
Published: December 2007

In a prospective cohort of 82 renal transplant recipients, we evaluated the capacity of the cytomegalovirus (CMV) load in whole blood (WB) to predict the plasma CMV load, aiming to identify active CMV infections by using WB samples only and to deduce a WB threshold. Using quantitative real-time PCR, a total of 1,474 WB samples were assayed, of which 279 were positive for CMV, and 140 out of the 276 paired plasma samples tested positive. Thirty (36.6%) patients presented with at least one positive plasma PCR result, and 21 infection episodes (19 patients) required curative treatment (median follow-up time, 12 months). When the plasma CMV load was >500 copies/ml (
n
= 70), more than 94% (95% confidence interval, 86.0%, 98.4%) of WB samples had >500 copies/ml. Two prediction models were built: log
10
plasma viral load (VL) was calculated as −0.3777 + 0.9342 × log
10
WB VL and as −0.3777 + 0.8563 × log
10
WB VL for patients with and without treatment, respectively. In the validation sample (578 routine samples), 77.2% of the observed and expected plasma viral loads were concordant (95% confidence intervals, 73.5 and 80.5%). According to the model, the plasma viral load was >500 copies/ml when the WB load was >3,170 or >4,000 copies/ml in patients with or without treatment, respectively. WB seems to be an appropriate candidate for routine CMV monitoring of transplant recipients by using a single assay.
Genetic Recombination between Human Immunodeficiency Virus Type 1 (HIV-1) and HIV-2, Two Distinct Human Lentiviruses
Authors: Motomura Kazushi , Chen Jianbo , Hu Wei-Shau
Published: December 2007

Human immunodeficiency virus type 1 (HIV-1) and HIV-2 are genetically distinct viruses that each can cause AIDS. Approximately 1 million people are infected with both HIV-1 and HIV-2. Additionally, these two viruses use the same receptor and coreceptors and can therefore infect the same target cell populations. To explore potential genetic interactions, we first examined whether RNAs from HIV-1 and HIV-2 can be copackaged into the same virion. We used modified near-full-length viruses that each contained a green fluorescent protein gene (
gfp
) with a different inactivating mutation. Thus, a functional
gfp
could be reconstituted via recombination, which was used to detect the copackaging of HIV-1 and HIV-2 RNAs. The GFP-positive (GFP
+
) phenotype was detected in approximately 0.2% of the infection events, which was 35-fold lower than the intrasubtype HIV-1 rates. We isolated and characterized 54 GFP
+
single-cell clones and determined that all of them contained proviruses with reconstituted
gfp
. We then mapped the general structures of the recombinant viruses and characterized the recombination junctions by DNA sequencing. We observed several different recombination patterns, including those that had crossovers only in
gfp
. The most common hybrid genomes had heterologous long terminal repeats. Although infrequent, crossovers in the viral sequences were also identified. Taken together, our study demonstrates that HIV-1 and HIV-2 can recombine, albeit at low frequencies. These observations indicate that multiple factors are likely to restrict the generation of viable hybrid HIV-1 and HIV-2 viruses. However, considering the large coinfected human population and the high viral load in patients, these rare events could provide the basis for the generation of novel human immunodeficiency viruses.
Functional Analysis of the Murine Cytomegalovirus Chemokine Receptor Homologue M33: Ablation of Constitutive Signaling Is Associated with an Attenuated Phenotype In Vivo
Authors: Case Ruth , Sharp Emma , Benned-Jensen Tau , Rosenkilde Mette M. , Davis-Poynter Nicholas , Farrell Helen E.
Published: December 2007

The murine cytomegalovirus (MCMV) M33 gene is conserved among all betaherpesviruses and encodes a homologue of seven-transmembrane receptors (7TMR) with the capacity for constitutive signaling. Previous studies have demonstrated that M33 is important for MCMV dissemination to or replication within the salivary glands. In this study, we probed N- and C-terminal regions of M33 as well as known 7TMR signature motifs in transmembrane (TM) II and TM III to determine the impact on cell surface expression, constitutive signaling, and in vivo phenotype. The region between amino acids R340and A353of the C terminus was found to be important for CREB- and NFAT-mediated signaling, although not essential for phosphatidylinositol turnover. Tagging or truncation of the N terminus of M33 resulted in loss of cell surface expression. Within TM II, an F79D mutation abolished constitutive signaling, demonstrating a role, as in other cellular and viral 7TMR, of TM II in receptor activation. In TM III, the arginine (but not the asparagine) residue of the NRY motif (the counterpart of the common DRY motif in cellular 7TMR) was found to be essential for constitutive signaling. Selected mutations incorporated into recombinant MCMV showed that disruption of constitutive signaling for a viral 7TMR homologue resulted in a reduced capacity to disseminate to or replicate in the salivary glands. In addition, HCMV UL33 was found to partially compensate for the lack of M33 in vivo, suggesting conserved biological roles of the UL33 gene family.
NANOSTRUCTURED AND SURFACE POLYMERIZED IRON PARTICLES FOR MAGNETORHEOLOGICAL FLUIDS
Authors: HU BEN , FUCHS ALAN , GORDANINEJAD FARAMARZ , EVRENSEL CAHIT
Published: December 2007

A novel magnetorheological fluid, in which the surface of iron particles is coated with poly (butyl acrylate) by surface initiated atom transfer radical polymerization (ATRP), is investigated. The polymer coating procedure includes two steps, which are immobilization of initiator: 2-4(-chlorosulfonylphenyl)-ethytrichlorosilane (CTCS) on the iron particles surface and graft polymerization of butyl acrylate from the surface. The surface coating is characterized by FTIR and SEM. This magnetorheological fluid has controllable off-state viscosity and high shear yield stress. Coating polymer on the iron particles surface by ATRP can significantly reduce iron particles settling and improve stability of the MR fluid. Polymerization kinetics of bulk butyl acrylate are investigated using differential scanning calorimetry (DSC). Glass transition temperature is obtained using the step-scan DSC method. The molecular weight and conversion can be controlled by the molar ratio of monomer to initiator, reaction temperature and time. The reaction is first order determined by the plot of In ( M / M 0) against polymerization time. The overall activation energy is found to be 126kJ/mol by Kissinger's Method.
INCREASING ELECTRORHEOLOGICAL RESPONSE OF PARTICLES: THE EFFECT OF CONDUCTIVE POLYMER
Authors: LENGÁLOVÁ ANEŽKA , PAVLÍNEK VLADIMÍR , CHENG QILIN , SÁHA PETR
Published: December 2007

The paper deals with the effect of two conductive polymers (polyaniline, PANI, and polypyrrole, PPy) in combination with inorganic particles on the response of silicone-oil suspensions. Conductive polymers cause a significant increase in electrorheological response. PANI combined with silica is much more efficient when in the form of a thin layer on the particle surface than if the two components are simply mixed. All combinations are followed from the viewpoint of viscosity and yield stress.
CATEGORICAL GROUPS, KNOTS AND KNOTTED SURFACES
Authors: MARTINS JOÃO FARIA
Published: December 2007

We define a knot invariant and a 2-knot invariant from any finite categorical group. We calculate an explicit example for the Spun Trefoil.
POSITIVE PRESENTATIONS OF SURFACE BRAID GROUPS
Authors: BELLINGERI PAOLO , GODELLE EDDY
Published: December 2007

We provide new group presentations for surface braid groups which are positive. We study some properties of such presentations and we solve the conjugacy problem in a particular case.
ELECTROMAGNETIC RADIATION FROM TEMPORAL VARIATIONS IN SPACE–TIME AND PROGENITORS OF GAMMA RAY BURST AND MILLISECOND PULSARS
Authors: JONES PRESTON
Published: December 2007

A time varying space–time metric is shown to be a source of electromagnetic radiation even in the absence of charge sources. The post-Newtonian approximation is used as a realistic model of the connection between the space–time metric and a time-varying gravitational potential. Rapid temporal variations in the metric from the coalescence of relativistic stars are shown to be likely progenitors of gamma ray burst and millisecond pulsars.
A MESHLESS ANALYSIS OF SHELLS BASED ON MOVING KRIGING INTERPOLATION
Authors: SAYAKOUMMANE VILAYSAK , KANOK-NUKULCHAI WORSAK
Published: December 2007

An Element Free Galerkin Method (EFGM) for the analysis of degenerated shell structures is presented. The method is based on the Moving Kriging (MK) Interpolation function. The properties of the interpolation function possess the Kronecker delta property. With the MK Interpolation function no additional treatment required at the boundary conditions compared with that of using Moving Least Square (MLS) approximation. This deficiency of MLS at boundary condition has been definitely eradicated. The membrane and shear locking in the numerical analysis for degenerated shell problems has been alleviated by using higher order and removed by using quartic order of polynomials. Numerical benchmark examples for shell structures are presented to validate the proposed approach.
BLIND AUDIO SEPARATION AND CONTENT ANALYSIS IN THE TIME-SCALE DOMAIN
Authors: JBARI ATMAN , ADIB ABDELLAH , ABOUTAJDINE DRISS
Published: December 2007

In this paper, we address the problem of Blind Audio Separation (BAS) by content evaluation of audio signals in the Time-Scale domain. Most of the proposed techniques rely on independence or at least uncorrelation assumption of the source signals exploiting mutual information or second/high order statistics. Here, we present a new algorithm, for instantaneous mixture, that considers only different time-scale source signature properties. Our approach lies in wavelet transformation advantages and proposes for this a new representation; Spatial Time Scale Distributions (STSD), to characterize energy and interference of the observed data. The BAS will be allowed by joint diagonalization, without a prior orthogonality constraint, of a set of selected diagonal STSD matrices. Several criteria will be proposed, in the transformed time-scale space, to assess the separated audio signal contents. We describe the logistics of the separation and the content rating, thus an exemplary implementation on synthetic signals and real audio recordings show the high efficiency of the proposed technique to restore the audio signal contents.
CROSS-GENRE FEATURE COMPARISONS FOR SPOKEN SENTENCE SEGMENTATION
Authors: CUENDET SEBASTIEN , HAKKANI-TUR DILEK , SHRIBERG ELIZABETH , FUNG JAMES , FAVRE BENOIT
Published: December 2007

Automatic sentence segmentation of spoken language is an important precursor to downstream natural language processing. Previous studies combine lexical and prosodic features, but can impose significant computational challenges because of the large size of feature sets. Little is understood about which features most benefit performance, particularly for speech data from different speaking styles. We compare sentence segmentation for speech from broadcast news versus natural multi-party meetings, using identical lexical and prosodic feature sets across genres. Results based on boosting and forward selection for this task show that (1) features sets can be reduced with little or no loss in performance, and (2) the contribution of different feature types differs significantly by genre. We conclude that more efficient approaches to sentence segmentation and similar tasks can be achieved, especially if genre differences are taken into account.
Evidence for simultaneous contraction and extension at different crustal levels during the Caledonian orogeny in NE Greenland
Authors: Andresen A. , Rehnström E.F. , Holte M.
Published: December 2007

Leucogranites are common in the East Greenland Caledonides. Most granites cut across Caledonian contractional structures and have been interpreted as decompression melts related to late to post-orogenic collapse. To constrain the timing of the collisional event responsible for crustal thickening, zircon, monazite and xenotime were extracted from syn-contractional magmatic rocks from André Land, NE Greenland (73°N) and analysed using the U–Pb isotope dilution thermal ionization mass spectrometry method. The resulting ages range between 429 and 425 Ma. An age of 424 Ma on monazites from a kyanite–garnet–mica gneiss (granite melt source rock) is interpreted as dating late-stage metamorphism and migmatization in the area. A large syn-extensional granite pluton yielded an age of 429 ± 1 Ma. These ages, combined with field observations, demonstrate that subhorizontal upper crustal extension was contemporaneous with mid- to lower crustal subhorizontal contraction, and that the upper crustal strain field is not necessarily representative of the coeval strain fields in the middle and lower crust. The presence of 429–425 Ma migmatites and related intrusive rocks structurally above low-grade metasediments demonstrates that the late and post-tectonic leucogranites are not late orogenic but related to a separate early Caledonian tectonomagmatic phase predating Early Devonian nappe translation.
The role of photosynthesis and CO
2
evasion in travertine formation: a quantitative investigation at an important travertine-depositing hot spring, Le Zitelle, Lazio, Italy
Authors: Pentecost Allan , Coletta Pietro
Published: December 2007

Le Zitelle hot springs contain high concentrations of dissolved Ca and CO
2
and precipitate copious quantities of aragonite and calcite as travertine. A study of precipitation rates in the upper section of the stream was undertaken using marble tablets. This showed that: (1) precipitation rate increased with distance from the spring over the section studied; (2) the rate was positively correlated with flow, agreeing with previous experimental and theoretical studies; (3) precipitation rates during the day and night did not differ statistically. The last finding demonstrated a negligible effect of photosynthesis on travertine formation and was supported by further precipitation rate studies undertaken in clear and blackened tubes. This conflicts with previous work that suggested an important role for microbial photosynthesis in travertine deposition at Le Zitelle. The microbial flora consisted mainly of cyanobacteria (
Spirulina
) and photosynthetic bacteria, with smaller quantities of diatoms. The biomass in most of the travertine was extremely low and often endolithic. Carbon fixation rates were also low. A mass-balance calculation of carbon flow showed that of 100 units of dissolved carbon entering the stream section investigated, 51 units were lost to the atmosphere as CO
2
, 0.9 units were deposited as travertine, 0.09 units were fixed by photosynthesis and 48 units remained in the stream water. We conclude that most of the Zitelle travertine is formed abiotically, casting doubt on the supposed biotic origin of travertine at this and other Italian sites.
The transition from the continent to the ocean: a deeper view on the Norwegian margin
Authors: Scheck-Wenderoth M. , Raum T. , Faleide J.I. , Mjelde R. , Horsfield B.
Published: December 2007

We present a regional, crustal-scale, 3D structural model of the Norwegian continental margin integrating sedimentary and crustal layers from the continental and the oceanic domain. The model includes six sedimentary units, underlain on the continental side by a thinned crystalline crust and a lower-crustal high-velocity body. In the oceanic domain, three crustal layers (2AB, 3A and 3B), thickened at the continent–ocean transition (COT), are modelled below the post-breakup deposits. Two major rift phases with different rift axes (Late Jurassic–Early Cretaceous and Late Cretaceous–Early Tertiary) have caused post-Jurassic subsidence and post-depositional deformation of the pre-Cretaceous units. The modelled COT suggests that the pre-breakup rifting event was related to differential stretching focused at the outer margin and that breakup took place in a ‘base-up’ magmatic process as a continuation of underplating. For the earlier rift event, stretching was distributed over the entire margin and led to accumulation of up to 12 km of Cretaceous deposits. The large sediment thickness of the Cretaceous units requires deep-water conditions and abundant sediment supply and thus coeval offshore subsidence and onshore uplift. All layers indicate a sinistral offset along the Jan Mayen Fracture Zone and its continentward continuation.
U–Pb zircon geochronology of plagiogranites from the Lough Nafooey (= Midland Valley) arc in western Ireland: constraints on the onset of the Grampian orogeny
Authors: Chew David M. , Graham John R. , Whitehouse Martin J.
Published: December 2007

The timing of peak Grampian metamorphism is well constrained from the detrital record of the adjacent fore-arc basin fill and geochronology of synorogenic intrusive rocks, but the onset of collision is less certain. Proximal Silurian conglomerates contain plagiogranite boulders unequivocally derived from the Lough Nafooey arc, two of which yield U–Pb secondary ionization mass spectrometry zircon ages of 489.9 ± 3.1 Ma and 487.8 ± 2.3 Ma. Nd isotopic evidence (ϵ
Nd(490)
c
. 0) demonstrates that the plagiogranites assimilated significant amounts of old continental crust. This provides an absolute age constraint on a previously poorly constrained and inferred event, demonstrating that the arc had encountered subducting Laurentian margin sediments by 490 Ma.
Marine diversity through the Phanerozoic: problems and prospects
Authors: SMITH ANDREW B.
Published: December 2007

The fossil record provides direct evidence of how diversity has changed over time, but cannot be taken at face value. Diversity curves constructed from counting taxa in the rock record are seriously biased by unevenness of geographical and stratigraphical sampling effort, inequality in the rock record available for sampling, and inconsistent taxonomic practice. Sample standardization removes some bias, but does not overcome more general incompleteness problems. Modelling that accounts for potential biases is a newer approach but needs accurate estimates of rock record and consistent taxonomic data. Uncertainty remains over whether the steep rise in diversity over the last 100 Ma is real or reflects sampling bias. The repeated rise and fall of marine diversity over time correlates closely with the areal extent of sedimentary deposits and independent estimates of the quality of the fossil record, implying a common driving factor, namely tectonically mediated sea-level change. However, whether changes in diversity are primarily biological in origin, or reflect sampling artefact, remains contentious. There is a distinct possibility that many of the apparent rises and falls in diversity over the Phanerozoic, including most of the ‘mass extinctions’, arise either partially or entirely from rock record bias.
Are relay ramps conduits for fluid flow? Structural analysis of a relay ramp in Arches National Park, Utah
Authors: Rotevatn Atle , Fossen Haakon , Hesthammer Jonny , Aas Tor E. , Howell John A.
Published: December 2007

Relay ramps associated with overlapping faults are commonly regarded as efficient conduits for fluid flow across potentially sealing intra-reservoir fault zones. The current study demonstrates that structural heterogeneity in the often anomalously wide damage zone of relay ramps may represent potential baffles to intra-ramp fluid flow. A network of ramp-parallel, ramp-diagonal and curved cataclastic deformation bands causes compartmentalization of the ramp studied in Arches National Park, Utah. Harmonic average calculations demonstrate that, although single deformation bands have little or no effect on effective permeability, the presence of even a very small number of low-permeable deformation band clusters could reduce along-ramp effective permeability by more than three orders of magnitude. Thus, although relay zones may maintain large-scale geometric communication, the results of this study demonstrate that caution must be exercised when considering relay ramps as fluid conduits across sealing faults in a production situation. Although relay ramps clearly represent effective migration pathways for hydrocarbons over geological time, the extent to which they conduct fluids in a production situation is more uncertain. Quantitative approaches include adjusting the transmissibility multipliers for faults in reservoir models to allow for increased cross-fault flow. If, however, the effect of internal structural heterogeneity is not taken into consideration, this type of adjustment may lead to gross overestimation of the effect of relay ramps. Sedimentology, stratigraphy, burial history and deformation mechanisms are some of the controlling factors for the formation of such structural heterogeneities.
The scaling of fracture compliance
Authors: Worthington M. H. , Lubbe R.
Published: December 2007

The seismic visibility of fractures depends on the magnitude of their normal and shear compliance and how these quantities vary with the scale of the fracture and depth of burial. Reliable estimates of fracture compliance as a function of confining pressure, in the range 10
-13
–10
-14
m Pa
-1
, have been obtained from laboratory measurements on core samples. The possibility of fractal scaling of fracture parameters has been proposed, in which case fracture compliance might be expected to increase with the scale of the fracture. Laboratory and field estimates of fracture compliance are presented covering a range of fracture sizes. Compliance is shown to increase with the scale of the fractures. Results obtained are broadly consistent with the magnitudes predicted from linear slip theory, in which the displacement discontinuity across a partially sealed interface is linearly related to the traction on the interface.
The Machar Oil Field: waterflooding a fractured chalk reservoir
Authors: Casabianca D. , Jolly R. J. H. , Pollard R.
Published: December 2007

The Machar Oil Field is a fractured Chalk Group reservoir, of Late Cretaceous age, developed above a salt diapir in the Central Graben of the UK Continental Shelf. From 1998 to the present the field has been produced through a water injection scheme sanctioned on the basis of data acquired during a water injection pilot test carried out in 1996. After three years of strong production, performance was affected by an unexpectedly fast rise in water-cut. This prompted the field management team to review the available data and rebuild the reservoir model to serve as the basis for a revised development plan. This paper describes the data used and the lines of evidence followed by the team in order to identify, describe and model the key subsurface characteristics, and related uncertainties, controlling field behaviour and impacting reservoir management and development options. Key uncertainties are the nature and flow significance of an extensive network of faults, the presence, nature and significance of a system of sub-seismic background fractures and the role played by the matrix capillary and wettability properties in controlling recovery through imbibition levels and rates. The successful integration of a wide range of subsurface static data, such as biostratigraphy, fracture identification, stress identification, seismic fault mapping and dynamic data, such as production logs, pressure build-up tests and tracer recovery, resulted in improved reservoir characterization. The ensuing new reservoir model explained the field historic performance and suggested two redevelopment options, which were sanctioned and executed between 2003 and 2004, and resulted in improved field performance.
Integrating discrete fracture network models and pressure transient data for testing conceptual fracture models of the Valhall chalk reservoir, Norwegian North Sea
Authors: Rogers S. , Enachescu C. , Trice R. , Buer K.
Published: December 2007

The Valhall Field is an Upper Cretaceous chalk reservoir located in the Central Graben area of the North Sea with production coming from the fractured Tor and Hod formations. Well tests and production history indicate that these formations are highly heterogeneous and that significant fluid flow occurs through both the matrix and fracture system. However there remained significant uncertainty about the specific controls and location of the main productivity conduits and how they would influence sweep efficiency during planned water flood. To address these uncertainties a range of possible conceptual fracture models were considered with respect to controls on major flow within the reservoir. Analysis indicated that the reservoir is dominated by a connected series of seismic scale faults acting as major flow conduits with smaller fractures providing a less significant enhancement to matrix permeability. A key input to this study was the examination of over 80 well tests. Simulation of a number of key well tests using a simple discrete fracture network model comprising a connected fault network and pseudo-matrix layer was able to reproduce the majority of the observed pressure derivative shapes. This gave some confidence to the understanding of major reservoir flow paths as well as providing calibrated fault properties for direct inclusion within the simulation model.
Characterizing fracture and matrix heterogeneities in folded Devonian carbonate thrust sheets, Waterton tight gas fields, Western Canada
Authors: Rawnsley K. , De Keijzer M. , Wei L. , Bettembourg S. , Asyee W. , Massaferro J.-L. , Swaby P. , Drysdale D. , Boettcher D.
Published: December 2007

Well performance is extremely variable in the stacked sequence of relatively tight Devonian and Mississippian carbonates in the northern part of the Waterton Complex, Alberta, Canada. This is despite having an extensively developed fracture system present in all the wells. In order to determine why some wells penetrated more permeable fractures than others, a full reinterpretation of the geophysical, structural, stress, matrix and dynamic data sets was carried out. Flow simulations at sector scales using discrete fracture network models and fullfield continuum modelling were used to test a range of geological and dynamic scenarios. One of the most northwestern fields of the Waterton complex, the West Carbondale field, is the focus of the work presented. For this field the best-fit dynamic models consist of a major fracture zone, corresponding to either a seismic scale lineament or zone of enhanced curvature, trending through the area of most prolific wells. Outside this zone, the vast majority of the fracture system makes little contribution to the flow in the wells, other than slightly enhancing the reservoir permeability.
Diagnosing decay: the value of medical analogy in understanding the weathering of building stones
Authors: Smith B. J. , Přikryl R.
Published: December 2007

This paper represents the first element of the introduction to this volume, and as such investigates its principal underlying rationale; namely the importance of accurate diagnosis of stone decay in the formulation of effective conservation strategies. It does this by exploring ways in which perceived similarities between stone decay and human disease have influenced attitudes towards conservation, and how refinements within medical diagnostic strategies can inform future condition assessments of building stones. In doing so, it identifies the importance of looking beyond obvious symptoms to the isolation of the fundamental causes of decay and the factors that control them. These controls are strongly conditioned by accumulated stresses within the stonework. In many buildings these are the product of a complex history involving exposure to a variety of environmental conditions and successive human intervention. Only by understanding these memory effects is it possible to explain current decay phenomena, attempt any prediction of future behaviour or recommend appropriate intervention. The concept of appropriateness is further developed through an examination of the TNM (Tumours, Nodes and Metastases) Staging System for cancer diagnosis. This holistic scheme embodies a progressive approach to diagnosis that begins with a clinical assessment based on how the patient presents, and leads on to more detailed pathological investigations involving sampling, testing and analysis. The scheme also requires an assessment of the certainty of the diagnosis and proposed treatments must be viewed in terms of a cost benefit analysis. A modified version of this staging system has already been developed for use in the physical assessment of buildings. It is suggested that the next stage in its development, and that of any other condition assessment procedure that deals solely with the fabric of a building, is the inclusion of a value-based appraisal of its cultural significance.
Natural stone portals of the town of Udine (Italy): their design, construction and materials between the 15th and 20th centuries
Authors: Frangipane Anna
Published: December 2007

The research focuses on the features of 250 natural stone portals of the civil buildings of the town of Udine (NE Italy), dating between the 15th and 20th centuries. In order to clearly define the number, characteristics and uniqueness of these architectural elements, three strategies were implemented: (i) a concise database of all the portals; (ii) a concise reference database of more than 100 portals of five significant nearby towns; and (iii) a detailed inventory, consisting of data and photographs of about 200 portals selected for relevance or because they represent a recurrent type. The analysis of the data collected, supported by reference studies of quarry location, stone-cutter activity, the work of architects, cultural relationships with immediate and distant influences permitted the definition of an interdisciplinary framework describing the main features of portal production, as related to formal evidence, stone materials, historical building and carving techniques. The rational organization of the huge set of data collected represents an effective working tool, interconnecting different aspects of the portals' realization, which was indispensable for the research, but will also be useful for further research on the role of stone material in the historic buildings of Udine.
The dimension stone potential of Thailand — overview and granite site investigations
Authors: Hoffmann A. , Siegesmund S.
Published: December 2007

The production of dimension stones is well established in Thailand and the country has considerable processing capacities in the region, second only to China. The geological background of Thailand provides a huge potential of dimension stones, including magmatic, metamorphic and sedimentary rocks. The NE part of the country is made up by the Khorat Plateau with the main sandstone resources at its western margin. Metamorphic carbonate rocks are predominantly distributed along the border of a basin area in central Thailand. The western part of the country is characterized by magmatic belts that comprise the resources of igneous rocks. Large quantities of the dimension stone potential were used in the first part of the 1990s, when the domestic economy underwent a considerable upturn. The most important region for the production of granitoid rocks is the Tak batholith in northern Thailand. Therefore, the Tak granitoids are discussed as a case study with respect to petrophysical and depositional characteristics.
Photo-based decay mapping of replaced stone blocks on the boundary wall of Worcester College, Oxford
Authors: Thornbush M. J. , Viles H. A.
Published: December 2007

In this study on the boundary wall of Worcester College, Oxford, the decay mapping in Adobe Photoshop (DMAP) approach is introduced to test the use of simple daylight photographs in the long-term monitoring of stone decay. This is conducted primarily through measured changes in surface brightness and roughness based on close-up photographic images of walls. The Magic Wand Tool was applied to greyscale images in Lab Color Mode to select proportions of pixels with a lightness (
L
) value of 77%. This paper shows the effectiveness of the calibration procedure used to validate lightness between surveys so that cross-temporal comparisons have a greater validity. It also outlines and discusses errors associated with the method as well as its limitations. The DMAP approach proves to be particularly useful when applied to long-term monitoring exceeding 5 years of survey.
The weathering and weatherability of Basílica da Estrela stones, Lisbon, Portugal
Authors: Figueiredo C. A. M. , Aires-Barros L. , Basto M. J. , Graça R. C. , Maurício A.
Published: December 2007

This paper presents a study of stone decay on the Basílica da Estrela, the most famous 18th century monument in the city of Lisbon, Portugal. It was built with Jurassic and Cretaceous limestones from the surroundings of Lisbon. Different approaches were used to establish the typology, causes and processes of the major weathering forms. Limestone samples from ancient quarries, salt efflorescences and disintegrated stone material from the interior of the church were characterized by chemical, mineralogical and petrographical analyses. Limestone physical properties related to fluid percolation were also determined. Detailed surveys of stone decay phenomena were carried out on the monument. Textures of grey-level images representative of the weathering forms were analysed by image analysis through covariance and granulometry operators. An HIDSPEC computational hydrogeochemical model, phase and graphical diagrams, and multivariate statistical analysis were used for water-rock interaction studies. Physical weathering forms prevail inside the church. The yellow Cretaceous limestone is the most deteriorated stone. This observation compares well with its intrinsic properties. The weathering is determined by the stone structures, such as stilolytes and fossils, and architectural features (geometry and surface finish). Soluble salts such as trona and thenardite were only found in a very small area inside the church.