bluuebunny/crossref_metadata_2025 huggingface dataset:
The risk for thromboembolic disease in lupus anticoagulant patients due to pathways involving P-selectin and CD154
Authors: Stamer Kathrin , Vormittag Rainer , Skeate Robert , Wahi Monika , Bugert Peter , Pabinger Ingrid , Panzer Simon
Published: March 2007

Individuals with lupus anticoagulants (LA) are at risk for thromboembolism(TE). Chronic inflammation is an important characteristicin LA patients which may dispose for TE. Platelets play akey role in inflammation and TE. We therefore investigated genepolymorphisms as well as plasma levels of platelet receptors aspredictors of TE in 107 LA patients. We compared 74 patientswith a history of thromboembolic disease (TE+),56 with venousthrombosis (VT), 12 with arterial thrombosis (AT), and six patientswho had both, with 33 LA patients without previousthrombosis (TE-).The P-selectin Pro715 allele was slightly morefrequent inVT (OR=3.167,95 % CI 0.955–10.503;p=0.0594),butno patient with AT had this allele (OR=0.099, 95 % CI0.001–0.790; p=0.0238) which therefore may protect from AT. Plasma levels of P-selectin, collected a median of 35 months(range 2–329 months) after the last thrombotic event, werehigher in patients withVT (p=0.0096) than inTE-,but not withAT(p=0.4713).These high P-selectin levels were not explained bythe P-selectin polymorphism. The CA repeat polymorphism inthe 3’-noncoding region of CD154 was significantly associatedwith the development of AT (OR=4.035, 95 % CI 1.329–12.249;p=0.0138). Plasma levels of CD154 were not significantly differentamong the subgroups. Thus, theThr715Pro polymorphism ofP-selectin and CA repeats of CD154 are differentiating betweenthe risk for VT and AT. Further, soluble P-selectin is elevated inLA patients with previousVT, but its role to predictVT needs to be evaluated in prospective studies.
The Element of Irrationality: Max Weber's Diagnosis of Modern Culture
Authors: Gronow Jukka
Published: March 2007

Max Weber's diagnosis of modern culture as presented for example in Science as Vocation includes the idea of differentiation between the spheres of science, art, and law and ethics But Weber also claims that all genuine values have gone from public life The parallel processes of rationalization and intellectualization have resulted in a loss of individual freedom and meaning This diagnosis does not simply follow from his over-narrow concept of rationality, as claimed by Habermas To Weber rationalization is not identical with the increase of instrumental rationality Rather, it is the formal and abstract, or quantifying nature of the modern type of rationality which is totally alien to all value considerations In Weber's opinion there is thus an unavoidable element of irrationally inherent in the very process of rationalization Weber obviously also wanted to emphasize the paradoxical nature of legal authority and formal bureaucracy The legitimacy of the modern type of domination does not rest on any shared norms or values, but is by nature exclusively procedural and formal An analysis of Weber's views about modernity thus reveals a highly conscious critique of the Project of Enlightenment
Bearing Bad News
Authors: McClenahen Lachlan , Lofland John
Published: March 2007

Occupations differ in the frequency with which their performers must communicate bad news to a serviced public. At one extreme, bad news must be communicated several times a day, day after day. One such occupation, the deputy U.S. Marshal, is analyzed in terms of tactics employed to manage the stressful moments of preparing to deliver bad news, delivering it, and shoring up recipients after delivery. Detailed tactics described include distancing, presaging, treating as routine, manipulating the message, and displaying certain supportive attitudes in interaction.
Aluminum Salt Catalysts in Durable-Press Finishing Treatments
Authors: Kullman Russell M.H. , Reinilardt Robert M.
Published: March 2007

Because of dangers to the environment from disposal of solutions containing heavy metals, the textile chemical finishing industry has become more interested in catalysts based on light metals for durable-press treatments. During a broad study of catalysis in reactions between cellulose and N-methylolamide cross-linking agents, aluminum salts were recog nized as particularly effective catalysts for such treatments. Various types of aluminum salts and complexes were evalu ated to produce wrinkle-resistant cotton-containing fabrics. Among aluminum compounds investigated, alone and in combinations, were inorganic salts, basic inorganic salts, simple and polycarboxylic organic salts, phase-separation salts, and urea-complex salts. The powerful activity of many of these aluminum catalysts lowers the energy requirement of processing by promoting the finishing reactions at lower-than-usual temperatures or in very short treatment times at higher temperatures
West Germany
Authors: Von Beyme Klaus
Published: March 2007

Germany, a socially homogenous federation, with a centralized party system, developed close cooperation between governments: central to state and state to state, facilitated by the hobnobbing of bureaucrats and politicians. Tax equalization headed off regional movements, so conflicts were really between parties because party ideologies and programs make a difference. Federalism acted as a barrier to rapid change.
To Biopsy or Not to Biopsy in suspected Herpes Simplex Encephalitis
Authors: Sawyer John , Ellner Jerrold , Ransohoff David F.
Published: March 2007

The authors performed a decision analysis to determine whether a patient suspected to have herpes simplex encephalitis (HSE) should undergo a brain biopsy or be treated empirically with medical therapy. In most cases, empiric treatment with acyclovir would be slightly favored; brain biopsy was not essential in management. However, brain biopsy was found useful for patients who had low CSF glucose at the time of initial lumbar puncture; such patients may have a very high risk to have other treatable conditions such as tuberculosis, brain abscess, toxoplasmosis, or cryptococcosis. The results of the analysis suggest that even with the advent of safe antiviral drug therapy such as acyclovir, brain biopsy is useful in a well-defined subset of patients with possible HSE. The rationale, however, is not to confirm HSE but rather to detect other treatable conditions. Key words: diagnosis; decision making; herpes simplex encephalitis. (Med Decis Making 8:95-101, 1988)
Sequential Decision Making with Continuous Disease States and Measurements
Authors: Schechter Clyde B.
Published: March 2007

The question of whether to perform a continuous valued test to assess a continuous valued health state such as blood pressure or serum cholesterol is explored by decision analysis. Principal assumptions are that the underlying health state and measurement variability are both normally distributed, and that the impact of treatment on the utility of outcomes varies linearly with the underlying health state. Using Bayes' theorem, an expression for the ex pected utility of performing the test is derived and compared with immediate treatment or decision to withhold treatment. The calculations can be carried out with a pocket calculator and a table of the normal distribution. Iterating the analysis, a sequential decision making process is developed, leading to a series of no treat/test again and test again/treat thresholds with which a running average of independently obtained measurements can be compared to produce stepwise optimal results. The thresholds are readily calculated on a microcom puter. Finally, the conjugate-normal-linear model is extended to encompass the correlated observations that may be made on a single visit. This paper concentrates on the mathematics of decision making with continuous variables. The companion paper illustrates its application to diastolic blood pressure.
Thermal Analysis of Some Organo Bromides as Potential Flame Retardants for Poly(Ethylene Terephthalate
Authors: Day M. , Wiles D.M.
Published: March 2007

A technique capable of simultaneously monitoring bromide ions and an asso ciated weight loss of organic bromides when heated with an infrared heater chosen to reflect conditions similar to those encountered in the burning pro cess is described. The technique has been applied to a range of aliphatic and aromatic bromine compounds in order to evaluate their potential as candidate gas-phase combustion inhibitors for poly/ethylene terephthalate).
Sport in Vampire Society
Authors: Heinemann Klaus , Puig Nuria
Published: March 2007

Despite the impressive array of claims and accomplishments, it is our view that sociologists in general, and sport sociologists in particular, are extremely conservative in the challenges they choose to undertake. Sport sociologists have therefore confined their research activities to only the most obvious phenomena. A wide spectrum of questions, issues and problems numerous theoretically important and questions of practical consequence remain unanswered.

In this article we use the results from some of our most recent research concerning sport in vampire society to indicate at least partial answers to some fundamental questions. In an empirical investigation using a questionnaire to 43 vampires (20 male, 23 female) we were able to point out that sport culture in vampire society depends on the specific way of life, nutrition and body existence found in that society. Sport is a mirror of society and the physical conditions of the beings therein. A factor analysis did not support a dichotomy but printed out four dimensions of the meaning of sport in vampire society.
Department Chairs' Perceptions of the Importance of Business Communication Skills
Authors: Wardrope William J.
Published: March 2007

The purpose of this investigation was to determine business department chairs' rat ings of topics typically covered in the business communication course. A sample of 280 chairs provided administrative information about the business communication courses at their institutions, rated the importance of 34 topics typically covered in the course, and assessed the need for the course in their programs. Results indicate that department chairs perceive writing skills to be more important to business communication courses than other communication skills, such as speaking, tech nology-mediated communication, interpersonal communication, team/group com munication, listening, and cultural literacy skills. Implications for business com munication curriculum and research are offered.
Influence of composition on mechanical properties of strawberry gels. Compression test and texture profile analysis / Influencia de la composición de geles de fresa en sus propiedades mecánicas. Pruebas de compresión y análisis de perfil de textura
Authors: Hernández M.J. , Durán L. , Costell E.
Published: March 2007

Fruit gels were prepared containing four levels (20, 40, 60 and 80%) of strawberry pulp, four levels (0.5, 0.7, 0.9 and 1.1 %) of hydrocolloids (kappa-carrageenan plus locust bean gum, 1:1) and two levels (0, 10%) of sucrose. Their mechanical properties were analyzed by compression (failure stress and failure strain) and by texture profile analysis, TPA (hardness, cohesiveness, springiness, adhesive ness, and chewiness). Addition of hydrocolloids produced expected increases in both stress and strain at failure. Sucrose increased failure stress but did not alter strain values. Increasing the pulp content from 20 to 80% resulted in a slight increase in stress and clearly lowered strain at failure. Fruit pulp addition produced increasing hardness, chewiness and adhesiveness values, and lowered cohesive ness and springiness. MANOVA analysis of TPA data showed that while gel hardness was mainly governed by hydrocolloid concentration, both cohesiveness and adhesiveness were clearly depen dent on the proportion of fruit pulp.
Digitalis Toxicity: Case Study
Authors: Benson Diane Sadler
Published: March 2007

This case study illustrates a major health care problem with the elderly: approximately 0.4-1 % of all U.S. hospital admissions involve digitalis toxicity. Assessment of risk factors, signs, and symptoms are outlined. Ongoing assessment by the home health nurse and the caregiver is key to preventing this problem. Teaching by the home health nurse is vital for the client on digitalis and his or her family. Home health care can make a major difference by assessing, teaching, and early referral for suspected toxicity.
Pseudoseizures in Social and Cultural Context
Authors: Yeh Eluen Ann
Published: March 2007

Pseudoseizures remain a common form of conversion symp tom worldwide, particularly among patients with co-existing epilepsy. This paper reviews current biomedical diagnostic and therapeutic approaches to pseudoseizures. It then com pares the individual-centred psychopathological accounts of pseudoseizures in biomedicine with anthropological accounts of other dissociative phenomena including behaviour in some possession cults. Two cases of pseudoseizures from a Japanese neuropsychiatric hospital illustrate the role of family, social and political-economic factors in chronicity. These examples demonstrate the need for a social perspective in research on pseudoseizures.
Historical and comparative perspectives on the Australian welfare state: a response to Rob Watts
Authors: Castles Francis G.
Published: March 2007

In response to Rob Watts' critique of my work as being that of a non-historian and as being structural-functionalist in orientation, I simply plead guilty. I suggest, however, that there are extenuating circumstances in the fact that my work on the Australian welfare state is in no way intended to be a contribution to historical studies, but is rather a contribution to comparative social policy research utilising the proper sociological tools for that task. On the other hand, I plead wholly innocent of Watts' other charge that my research findings have somehow deflected Australian historians from their proper research tasks. In the absence of any evidence to the contrary—and Watts provides none—any defects in the work of historians of the Australian welfare state must be attributed to the deficiencies of that discipline and its practitioners, not to the influence of non-historians such as myself.
The Australian middle class, 1986-1995: stable, declining or restructuring?
Authors: Martin Bill
Published: March 2007

This article uses Australian Bureau of Statistics data to examine the changing fortunes of the professional-managerial middle class in Australia between the mid-1980s and the mid-1990s. It examines employment levels, gender patterns of employment, and relative earnings amongst professional and managerial workers. Results show considerable variation between occupational groups, though there is little evidence of the general 'crisis' of the middle class diagnosed by some writers. The complex picture suggests several patterns. First, there is a tendency for the more private sector, market-oriented occupations (such as private sector managers and 'business professionals') to have experienced rising employment levels and relative earnings, especially in the second half of the period, while more state dependent occupations have faced the opposite. Second, and cross-cutting the first tendency, lower level managers have fared far less well than upper level ones, indicating an increasing bifurcation in managerial ranks. Third, some heavily state dependent professional groups, particularly those with elite professional status or strong trade union-like organisation, have been quite successful in resisting the negative impacts of the squeeze on the state sector. Finally, feminisation of all middle class occupations has continued apace throughout the period, although from highly variable starting points.
Restoring Justice
Authors: Savage Stephen P.
Published: March 2007

Miscarriages of justice in Britain have been exposed as injustices largely as a result of public campaigns by victims of miscarriages and by the families and associates of those victims. This study, based on empirical research on those involved with justice campaigns, examines the motivational forces behind justice campaigns and the goals that justice campaigners seek to achieve. In doing so it applies the conceptual framework and principles of restorative justice as a means of interpreting the motivations behind justice campaigns, and in particular the principles of victim participation, dialogue, communication, apology, healing and future orientation. It concludes that, insofar as justice campaigns exhibit restorative justice principles, this is very much a one-sided process, because the ‘offenders’ in miscarriages of justice - the state and state institutions - are reluctant to accept guilt or acknowledge failure.
The Role of Self-Control in Crime Causation
Authors: Wikström Per-Olof H. , Treiber Kyle
Published: March 2007

In this paper we present an alternative conception of self-control and its role in crime causation to the one advanced by Gottfredson and Hirschi (1990) in their influential General Theory of Crime. Our conception is based on the theoretical framework outlined in the situational action theory of crime causation (e.g. Wikström 2006a). We propose that self-control is best analysed as a situational concept (a factor in the process of choice) rather than as an individual trait. We suggest that the core individual trait influencing an individual's ability to exercise self-control is executive capability. We maintain that there are also important environmental influences on an individual's ability to exercise self-control. We submit that the ability to exercise self-control is a relevant factor in crime causation only in situations where an individual considers (deliberates) whether or not to engage in an act of crime. We argue that for most people (in most circumstances) whether or not they engage in acts of crime is not a question of their ability to exercise self-control but rather a question of their morality. In short, this paper aims to clarify the concepts of ‘executive capability’, ‘self-control’ and ‘crime’, and to specify their relationships and role in the explanation of crime.
Re-forming and Re-valuing Educational Administration: Whence and When Cometh the Phoenix?
Authors: Greenfield Thomas
Published: March 2007

At the IIP in Bristol in 1974 Tom Greenfield delivered a paper which profoundly challenged traditional thinking on theory and research within educational administration. Since then he has played a key role in the continuing debate on how we are to understand the nature of the field and has published a stream of articles which have developed and defended his position. This paper, written on the occasion of his retirement from the Ontario Institute of Educational Studies, represents a major review and restatement of his views on the fundamental problem of theory and knowledge in the field of educational administration and of the place of values in such an enquiry.
Direct inhibition of CD40L expression can contribute to the clinical efficacy of daclizumab independently of its effects on cell division and Th1/Th2 cytokine production
Authors: Snyder James T. , Shen Jijia , Azmi Hooman , Hou Jeannie , Fowler Daniel H. , Ragheb Jack A.
Published: March 2007

Humanized anti-CD25 antibodies (eg, daclizumab) have been successfully used to treat several autoimmune diseases. Paradoxically, IL-2 blockade in mice can induce autoimmunity. An interspecies difference in the relative contribution of IL-2 to CD25+ T regulatory cell (CD25+Treg) versus CD25+ effector cell function might explain this conundrum. Consistent with this are reports that daclizumab inhibits human CD25+ effector cell cytokine production by blocking the expression of CD40L. However, in mice, IL-4 and IL-12 regulate CD40L expression. As human Th1/Th2 cytokine production is also dependent on IL-2, daclizumab's inhibition of CD40L expression could be due to an indirect, rather than a direct, effect of IL-2. Here, we clarify the mechanisms underlying CD40L expression. In contrast to the mouse, human CD40L is regulated by CD28 signaling and IL-2, not the principal Th1/Th2-polarizing cytokines. We find that CD40L is expressed on naive and memory cells and inhibited by daclizumab independently of cell division. Collectively, our results indicate that daclizumab could inhibit CD25+ effector T-cell function in vivo by directly blocking CD40L expression. This difference between mice and human may help explain the paradoxical effects of IL-2R blockade in the 2 species.
A computational approach for detecting peptidases and their specific inhibitors at the genome level
Authors: Bartoli Lisa , Calabrese Remo , Fariselli Piero , Mita Damiano G , Casadio Rita
Published: March 2007

Background

Peptidases are proteolytic enzymes responsible for fundamental cellular activities in all organisms. Apparently about 2–5% of the genes encode for peptidases, irrespectively of the organism source. The basic peptidase function is "protein digestion" and this can be potentially dangerous in living organisms when it is not strictly controlled by specific inhibitors. In genome annotation a basic question is to predict gene function. Here we describe a computational approach that can filter peptidases and their inhibitors out of a given proteome. Furthermore and as an added value to MEROPS, a specific database for peptidases already available in the public domain, our method can predict whether a pair of peptidase/inhibitor can interact, eventually listing all possible predicted ligands (peptidases and/or inhibitors).

Results

We show that by adopting a decision-tree approach the accuracy of PROSITE and HMMER in detecting separately the four major peptidase types (Serine, Aspartic, Cysteine and Metallo- Peptidase) and their inhibitors among a non redundant set of globular proteins can be improved by some percentage points with respect to that obtained with each method separately. More importantly, our method can then predict pairs of peptidases and interacting inhibitors, scoring a joint global accuracy of 99% with coverage for the positive cases (peptidase/inhibitor) close to 100% and a correlation coefficient of 0.91%. In this task the decision-tree approach outperforms the single methods.

Conclusion

The decision-tree can reliably classify protein sequences as peptidases or inhibitors, belonging to a certain class, and can provide a comprehensive list of possible interacting pairs of peptidase/inhibitor. This information can help the design of experiments to detect interacting peptidase/inhibitor complexes and can speed up the selection of possible interacting candidates, without searching for them separately and manually combining the obtained results. A web server specifically developed for annotating peptidases and their inhibitors (HIPPIE) is available at http://gpcr.biocomp.unibo.it/cgi/predictors/hippie/pred_hippie.cgi
The BioPrompt-box: an ontology-based clustering tool for searching in biological databases
Authors: Corsi Claudio , Ferragina Paolo , Marangoni Roberto
Published: March 2007

Background

High-throughput molecular biology provides new data at an incredible rate, so that the increase in the size of biological databanks is enormous and very rapid. This scenario generates severe problems not only at indexing time, where suitable algorithmic techniques for data indexing and retrieval are required, but also at query time, since a user query may produce such a large set of results that their browsing and "understanding" becomes humanly impractical. This problem is well known to the Web community, where a new generation of Web search engines is being developed, like Vivisimo. These tools organize on-the-fly the results of a user query in a hierarchy of labeled folders that ease their browsing and knowledge extraction. We investigate this approach on biological data, and propose the so called The BioPrompt-boxsoftware system which deploys ontology-driven clustering strategies for making the searching process of biologists more efficient and effective.

Results

The BioPrompt-box (Bpb) defines a document as a biological sequence plus its associated meta-data taken from the underneath databank – like references to ontologies or to external databanks, and plain texts as comments of researchers and (title, abstracts or even body of) papers. Bpboffers several tools to customize the search and the clustering process over its indexed documents. The user can search a set of keywords within a specific field of the document schema, or can execute Blastto find documents relative to homologue sequences. In both cases the search task returns a set of documents (hits) which constitute the answer to the user query. Since the number of hits may be large, Bpbclusters them into groups of homogenous content, organized as a hierarchy of labeled clusters. The user can actually choose among several ontology-based hierarchical clustering strategies, each offering a different "view" of the returned hits. Bpbcomputes these views by exploiting the meta-data present within the retrieved documents such as the references to Gene Ontology, the taxonomy lineage, the organism and the keywords. Of course, the approach is flexible enough to leave room for future additions of other meta-information. The ultimate goal of the clustering process is to provide the user with several different readings of the (maybe numerous) query results and show possible hidden correlations among them, thus improving their browsing and understanding.

Conclusion

Bpb is a powerful search engine that makes it very easy to perform complex queries over the indexed databanks (currently only UNIPROT is considered). The ontology-based clustering approach is efficient and effective, and could thus be applied successfully to larger databanks, like GenBank or EMBL.
Soluble RAGE but not endogenous secretory RAGE is associated with albuminuria in patients with type 2 diabetes
Authors: Humpert Per M , Djuric Zdenka , Kopf Stefan , Rudofsky Gottfried , Morcos Michael , Nawroth Peter P , Bierhaus Angelika
Published: March 2007

Background

Total circulating soluble receptor for advanced glycation endproducts (sRAGE) and a more defined endogenous secretory splice variant of the receptor (esRAGE) were shown to be associated with different markers of cardiovascular risk in patients with diabetes. Since previous data were partly divergent, the aim of this study was to compare sRAGE and esRAGE in a head-to-head analysis in patients with type 2 diabetes (T2DM) with albuminuria.

Methods

sRAGE and esRAGE were studied in plasma of 110 T2DM patients using enzyme-linked immunosorbant assays (ELISA) detecting either sRAGE or esRAGE only. Both sRAGE and esRAGE were compared with regard to applicability as markers for vascular disease and glucose control in T2DM.

Results

In bivariate analysis, sRAGE correlated with age (R = 0.22, p = 0.02) and the 24 hour albumin excretion rate (R = 0.18, p = 0.05), while esRAGE correlated positively with age only (R = 0.23, p = 0.02). In contrast to previous reports, neither sRAGE nor esRAGE correlated with glucose control or intima-media-thickness (IMT) as a predictor of macrovascular disease. In multivariate regression models, the associations between sRAGE and albuminuria as well as esRAGE and age were shown to be independent of glucose control, diabetes duration, body-mass index, glomerular filtration rate, blood pressure and gender.

Conclusion

This is the first study comparing sRAGE and esRAGE as markers of vascular complications in patients with T2DM. sRAGE but not esRAGE is independently associated with albuminuria in these patients while neither sRAGE nor esRAGE are associated with markers of glucose control or macrovascular disease.
Irreversibility of cellular senescence: dual roles of p16INK4a/Rb-pathway in cell cycle control
Authors: Takahashi Akiko , Ohtani Naoko , Hara Eiji
Published: March 2007

The retinoblastoma (Rb) tumor suppressor gene product, pRb, has an established role in the implementation of cellular senescence, the state of irreversible G1 cell cycle arrest provoked by diverse oncogenic stresses. In murine cells, senescence cell cycle arrest can be reversed by subsequent inactivation of pRb, indicating that pRb is required not only for the onset of cellular senescence, but also for the maintenance of senescence program in murine cells. However, in human cells, once pRb is fully activated by p16INK4a, senescence cell cycle arrest becomes irreversible and is no longer revoked by subsequent inactivation of pRb, suggesting that p16INK4a/Rb-pathway activates an alternative mechanism to irreversibly block the cell cycle in human senescent cells. Here, we discuss the molecular mechanism underlying the irreversibility of senescence cell cycle arrest and its potential towards tumor suppression.
RESINVM3D: A 3D resistivity inversion package
Authors: Pidlisecky Adam , Haber Eldad , Knight Rosemary
Published: March 2007

We have developed an open source 3D, MATLAB based, resistivity inversion package. The forward solution to the governing partial differential equation is efficiently computed using a second-order finite volume discretization coupled with a preconditioned, biconjugate, stabilized gradient algorithm. Using the analytical solution to a potential field in a homogeneous half space, we evaluate the accuracy of our numerical forward solution and, subsequently, develop a source correction factor that reduces forward modeling errors associated with boundary effects and source electrode singularities. For the inversion algorithm we have implemented an inexact Gauss-Newton solver, with the model update being calculated using a preconditioned conjugate gradient algorithm. The inversion uses a combination of zero and first order Tikhonov regularization. Two synthetic examples demonstrate the usefulness of this code. The first example considers a surface resistivity survey with 3813 measurements. The discretized model space contains 19,040 cells. For this example, the inversion package converges in approximately [Formula: see text] on a [Formula: see text] Pentium 4, with [Formula: see text] of RAM. The second example considers the case of borehole based data acquisition. For this example there were 4704 measurements and 13,200 model cells. The inversion for this example requires [Formula: see text] of computational time.
Prestack depth migration of primary and surface-related multiple reflections: Part I — Imaging
Authors: Muijs Remco , Robertsson Johan O. , Holliger Klaus
Published: March 2007

Surface-related multiples (i.e., all seismic waves reflected at the free surface at least once) often severely contaminate seismic recordings. Because conventional imaging techniques require input data that consist of primary reflections only, significant processing effort is commonly dedicated to attenuating multiples prior to migration. On the other hand, surface-related multiples provide additional illumination of the subsurface and, therefore, should not be considered as noise. We present a prestack depth-migration method that allows primary and multiple reflections to be imaged simultaneously. Depth imaging using primary and multiple reflections (DIPMR) involves decomposing the datainto upgoing and downgoing wave constituents, followed by downward extrapolation. Artifacts generated by interference of upgoing and downgoing events not associated with the same subsurface reflection points (crosstalk) are attenuated by using a 2D deconvolution imaging condition. In contrast to existing methods, DIPMR does not require a priori information about the source signature or directivity, because the illuminating source wavefield is extracted directly from the data themselves via the up/down separation. Moreover, there is no need for elimination nor identification of multiples prior to migration. By including surface-related multiples in the imaging procedure, the effective source wavefield is stronger, the spatial aperture is wider, and a higher vertical resolution is enabled through the application of a deconvolution-based imaging condition.
Wavelet-Radon domain dealiasing and interpolation of seismic data
Authors: Yu Zhou , Ferguson John , McMechan George , Anno Phil
Published: March 2007

Spatial aliasing is unavoidable in some seismic data and has serious effects on the performance of multichannel data processing and migration. Antialias filtering produces distortion of the signal through the removal of high-frequency information. In contrast, dealiasing produces an unaliased estimate of the signal at all frequencies present in the original time series. A new dealiasing algorithm is developed by exploiting the properties of seismic wavefields in the wavelet-Radon transform domain, specifically the overlap of information between wavelet scales at the same frequency. The effectiveness of the wavelet-Radon dealiasing algorithm is demonstrated through the processing of both synthetic and field seismic data.
2D gravity inversion of a complex interface in the presence of interfering sources
Authors: Silva Dias Fernando J. , Barbosa Valeria C. , Silva João B.
Published: March 2007

We present a new semiautomatic gravity interpretation method for estimating a complex interface between two media containing density heterogeneities (referred to as interfering sources) that give rise to a complex and interfering gravity field. The method combines a robust fitting procedure and the constraint that the interface is very smooth near the interfering sources, whose approximate horizontal coordinates are defined by the user. The proposed method differs from the regional-residual separation techniques by using no spectral content assumption about the anomaly produced by the interface to be estimated, i.e., the interface can produce a gravity response containing both low- and high-wavenumber features. As a result, it may be applied to map the relief of a complex interface in a geologic setting containing either shallow or deep-seated interfering sources. Tests conducted with synthetic data show that the method can be of utility in estimating the basement relief of a sedimentary basin in the presence of salt layers and domes or in the presence of mafic intrusions in the basement or in both basement and the sedimentary section. The method was applied to real gravity data from two geologic settings having different kinds of interfering sources and interfaces to be interpreted: (1) the interface between the upper and lower crusts over the Bavali shear zone of southern India and (2) the anorthosite-tonalite interface over the East Bull Lake gabbro-anorthosite complex outcrop in Ontario, Canada.
Seismoelectric imaging of shallow targets
Authors: Haines Seth S. , Pride Steven R. , Klemperer Simon L. , Biondi Biondo
Published: March 2007

We have undertaken a series of controlled field experiments to develop seismoelectric experimental methods for near-surface applications and to improve our understanding of seismoelectric phenomena. In a set of off-line geometry surveys (source separated from the receiver line), we place seismic sources and electrode array receivers on opposite sides of a man-made target (two sand-filled trenches) to record separately two previously documented seismoelectric modes: (1) the electromagnetic interface response signal created at the target and (2) the coseismic electric fields located within a compressional seismic wave. With the seismic source point in the center of a linear electrode array, we identify the previously undocumented seismoelectric direct field, and the Lorentz field of the metal hammer plate moving in the earth’s magnetic field. We place the seismic source in the center of a circular array of electrodes (radial and circumferential orientations) to analyze the source-related direct and Lorentz fields and to establish that these fields can be understood in terms of simple analytical models. Using an off-line geometry, we create a multifold, 2D image of our trenches as dipping layers, and we also produce a complementary synthetic image through numerical modeling. These images demonstrate that off-line geometry (e.g., crosswell) surveys offer a particularly promising application of the seismoelectric method because they effectively separate the interface response signal from the (generally much stronger) coseismic and source-related fields.
Angle-domain common-image gathers from anisotropic migration
Authors: Biondi Biondo
Published: March 2007

I present a general methodology for computing angle-domain common-image gathers (ADCIGs) in conjunction with anisotropic wavefield-continuation migration. The method is based on transforming the prestack image from the subsurface-offset domain to the angle domain using slant stacks. The processing sequence is the same as that for computing ADCIGs for the isotropic case, though the interpretation of the relationship between the slopes measured in the prestack image and the aperture angles is more complex. I demonstrate that the slopes measured by performing slant stacks along the subsurface-offset axis of the prestack image provide a good approximation of the phase aperture angles, and they are exactly equal to the phase aperture angles for flat reflectors in vertical transversly isotropic (VTI) media. In the general case of dipping reflectors, the angles computed using slant stacks can be easily corrected by applying the relationships that I present in this paper, and the accurate aperture angles can be determined as a function of the reflector dip and anisotropic slowness at the reflector. I derive these relationships from both plane-wave and ray viewpoints. This theoretical development links the kinematics in ADCIGs with migration-velocity errors. I apply the proposed method to compute ADCIGs from the prestack image obtained by anisotropic migration of a 2D line recorded in the Gulf of Mexico. I analyze the error introduced by neglecting the difference between the true phase aperture angle and the angle computed through slant stacks, showing that, at least for this data set, these errors are negligible and can be safely ignored. In contrast, group aperture angles can be quite different from phase aperture angles; thus, ignoring the distinction between these two angles can be detrimental to practical applications.
2D marine controlled-source electromagnetic modeling: Part 2 — The effect of bathymetry
Authors: Li Yuguo , Constable Steven
Published: March 2007

Marine controlled-source electromagnetic (CSEM) data are strongly affected by bathymetry because of the conductivity contrast between seawater and the crust below the seafloor. We simulate the marine CSEM response to 2D bathymetry using our new finite element (FE) code, and our numerical modeling shows that all electric and magnetic components are influenced by bathymery, but to different extents. Bathymetry effects depend upon transmission frequency, seabed conductivity, seawater depth, transmitter-receiver geometry, and roughness of the seafloor topography. Bathymetry effects clearly have to be take into account to avoid the misinterpretation of marine CSEM data sets.
Stacking of surface waves
Authors: Neducza Boriszláv
Published: March 2007

The seismic surface wave method (SWM) is a powerful means of characterizing near-surface structures. Although the SWM consists of only three steps (data acquisition, determination of dispersion curves, and inversion), it is important to take considerable care with the second step, determination of the dispersion curves. This step is usually completed by spectral analysis of surface waves (SASW) or multichannel analysis of surface waves (MASW). However, neither method is ideal, as each has its advantages and disadvantages. SASW provides higher horizontal resolution, but it is very sensitive to coherent noise and individual geophone coupling. MASW is a robust method able to separate different wave types, but its horizontal resolution is lower. Stacking of surface waves (SSW) is a good compromise between SASW and MASW. Using a reduced number of traces increases the horizontal resolution of MASW, and utilizing other shot records with the same receivers compensates for the decreased signal-to-noise ratio. The stacking is realized by summing the [Formula: see text] amplitude spectra of windowed shot records, where windowing produces higher horizontal resolution and stacking produces improved data quality. Mixing is applied between the stacks derived with different parameters, as different frequency ranges require different windowing. SSW was tested and corroborated on a deep seismic data set. Horizontal resolution is validated by [Formula: see text] plots at different frequencies, and [Formula: see text] plots present data quality.
A simple design procedure for depth extrapolation operators that compensate for absorption and dispersion
Authors: Mittet Rune
Published: March 2007

I compensate for the effects of absorption and dispersion in deriving the space-frequency domain depth extrapolation operators by starting from the ones without such compensation. The procedure is simple and requires only trivial cosine transforms applied to the original noncompensating operators. I show that compensating operators enhance resolution as a function of depth when applied in prestack depth migration.
A field comparison of Fresnel zone and ray-based GPR attenuation-difference tomography for time-lapse imaging of electrically anomalous tracer or contaminant plumes
Authors: Johnson Timothy C. , Routh Partha S. , Barrash Warren , Knoll Michael D.
Published: March 2007

Ground-penetrating radar (GPR) attenuation-difference tomography is a useful tool for imaging the migration of electrically anomalous tracer or contaminant plumes. Attenuation-difference tomography uses the difference in the trace amplitudes of tomographic data sets collected at different times to image the distribution of bulk-conductivity changes within the medium. The most common approach for computing the tomographic sensitivities uses ray theory, which is well understood and leads to efficient computations. However, ray theory requires the assumption that waves propagate at infinite frequency, and thus sensitivities are distributed along a line between the source and receiver. The infinite-frequency assumption in ray theory leads to a significant loss of resolution (both spatially and in terms of amplitude) of the recovered image. We use scattering theory to approximate the sensitivity of electromagnetic (EM) wave amplitude to changes in bulk conductivity within the medium.These sensitivities occupy the first Fresnel zone, account for the finite frequency nature of propagating EM waves, and are valid when velocity variations within the medium do not cause significant ray bending. We evaluate the scattering theory sensitivities by imaging a bromide tracer plume as it migrates through a coarse alluvial aquifer over two successive days. The scattering theory tomograms display a significant improvement in resolution over the ray-based counterparts, as shown by a direct comparison of the tomograms and also by a comparison of the vertical fluid conductivity distribution measured in a monitoring well, located within the tomographic plane. By improving resolution, the scattering theory sensitivities increase the utility of GPR attenuation-difference tomography for monitoring the movement of electrically anomalous plumes. In addition, the improved accuracy of information gathered through attenuation-difference tomography using scattering theory is a positive step toward future developments in using GPR data to help characterize the distribution of hydrogeologic properties.
On the physics of the marine controlled-source electromagnetic method
Authors: Um Evan Schankee , Alumbaugh David Lee
Published: March 2007

We examine the underlying physics of the marine controlled-source electromagnetic (CSEM) method through the use of cross-sectional plots of the vector-current density. A systematic comparison of the cross-sectional current-density distribution within uniform and reservoir-bearing seafloor models reveals that the method induces detectable reservoir responses at the seafloor for source-receiver offsets that are frequency dependent. Higher frequencies generally result in larger anomalous differences between the two models at shorter offsets up to a frequency where induced currents no longer effectively interact with the reservoir due to electromagnetic (EM) attenuation. At zero and low frequencies, the less-attenuated background EM fields mask the reservoir response, although large induced currents are normally incident upon the reservoir. The reservoir response is also masked at larger offsets and/or in shallow environments by theairwave that can be thought of as energy diffusing up and down through the seawater column and propagating along the air-seawater interface. As the background EM fields and airwave are nearly horizontal because of the air-seawater boundary, vertical electric-field (E) measurements are free of the masking effect and, thus, might serve as additional useful information, especially in shallow environments where horizontal E measurements lose resolution of the reservoir. Horizontal magnetic field (B) measurements supplement the horizontal E measurements as E and B decay at different rates away from a source position in the near-field zone of a horizontal electric-dipole source. Comparison of CSEM responses for 1D and 3D reservoirs indicates that the 3D reservoir response is substantially smaller because of the limited surface area of the localized 3D reservoir, and that the pattern of the 3D reservoir response radically varies with a source position relative to reservoir boundaries.
Using CSEM techniques to map the shallow section of seafloor: From the coastline to the edges of the continental slope
Authors: Evans Rob L.
Published: March 2007

Many important processes occur within the shallow section of the seafloor on the continental shelf and slope, yet conventional geophysical constraints on the physical properties within this critical boundary layer are limited. Some of the key constraints involve quantification of fluids within the seafloor, which can be provided by electrical methods. This paper reviews the application of a towed EM system to map the uppermost [Formula: see text] of seafloor in a variety of settings ranging from nearshore regions in water depths of approximately [Formula: see text] on the continental shelf out to water depths of [Formula: see text]. The system is a mapping tool that provides areal maps of seafloor resistivity and has been used for a variety of purposes, including sedimentary characterization and facies mapping, evaluation of groundwater discharge, and mapping seafloor mounds in the Gulf of Mexico, thought to contain massive deposits of gas hydrate.
A Bayesian model for gas saturation estimation using marine seismic AVA and CSEM data
Authors: Chen Jinsong , Hoversten G. Michael , Vasco Donald , Rubin Yoram , Hou Zhangshuan
Published: March 2007

We develop a Bayesian model to jointly invert marine seismic amplitude versus angle (AVA) and controlled-source electromagnetic (CSEM) data for a layered reservoir model. We consider the porosity and fluid saturation of each layer in the reservoir, the bulk and shear moduli and density of each layer not in the reservoir, and the electrical conductivity of the overburden and bedrock as random variables. We also consider prestack seismic AVA data in a selected time window as well as real and quadrature components of the recorded electrical field as data. Using Markov chain Monte Carlo (MCMC) sampling methods, wedraw a large number of samples from the joint posterior distribution function. With these samples, we obtain not only the estimates of each unknown variable, but also various types of uncertainty information associated with the estimation. This method is applied to both synthetic and field data to investigate the combined use of seismic AVA and CSEM data for gas saturation estimation. Results show that the method is effective for joint inversion; the incorporation of CSEM data reduces uncertainty in fluid saturation estimation compared to inversion of seismic AVA data alone. The improvement in gas saturation estimation obtained from joint inversion for field data is less significant than for synthetic data because of the large number of unknown noise sources inherent in the field data.