bluuebunny/crossref_metadata_2025 huggingface dataset:
Marine downhole to seafloor dipole-dipole electromagnetic methods and the resolution of resistive targets
Authors: Scholl Carsten , Edwards R. Nigel
Published: March 2007

Most active marine electromagnetic surveys use an array of transmitting and receiving electric dipoles located on the sea-floor. There are many reports of successful detections of buried resistors with these arrays. Nevertheless, the concept has a significant drawback: Large offsets between the transmitter and receiver with respect to the target depth are needed. A logical alternative is the use of a vertical electric-dipole transmitter in a borehole deeper than the target, combined with receivers located at the seafloor. Because current must pass through the target, even data recorded at short offsets with respect to target depth should be sensitive to the target. We derived the equations for the electric and magnetic field components produced by the vertical electric dipole in a 1D layered medium. The equations are used to model the fields for resistive layers. An eigenparameter analysisis applied to the different field components, and the resolution is compared with the standard seafloor inline array. The analyses show that data for the downhole transmitter are more sensitive to the resistance between the source and the receiver than the sea-floor array. However, model geometry such as depth to the target is resolved less easily. The resolution of the model geometry is improved significantly when a long bipole transmitter is used, extended from below the target layer to a level above it. We carried out 3D modeling for the downhole transmitter through the use of a finite-difference algorithm. Results indicate that these data are very sensitive to lateral changes within the target layer. Differences between electric fields simulated at the seafloor for 3D models and a reference model show a correlation to lateral resistivity differences. This finding suggests that the array is suitable for mapping and monitoring resistivity anomalies outward from the borehole.
Multichannel, full waveform and flexible electrode combination resistivity-imaging system
Authors: Zhe Jingping , Greenhalgh Stewart , Marescot Laurent
Published: March 2007

The development of a new multichannel and multielectrode, full waveform resistivity acquisition system is presented. This system, which can be built in any electronics workshop without major difficulties, allows for large data collection capacity and flexibility but without the sacrifice of channels, as in most other systems that use a preselected array. A superior interpretation quality is enabled by the increased data and the monitoring of noise through full waveform display. The proposed hardware is robust because no electronics need to be installed in the cable. Therefore, it is suitable for 2D or 3D surface or crosshole tomography. A major feature of the data collection strategy is to capture all of the electrode combinations subject to having one current electrode in each cable. This is efficient because there is no extra cost in doing this. It is an automatic process; one does not have to make any prior decisions as to what electrode combinations to use. The data sets collected with this strategy are suitable for an inversion process involving a large amount of data because the number of voltage values measured using a couple of current electrodes is maximized. Synthetic modeling shows that the proposed approach allows for better imaging of the subsurface than with conventional arrays and the results are comparable to results obtained with an optimized experimental design strategy. A field experiment illustrates the effectiveness of the presented strategy. The inverted image of the subsurface is well-correlated with the available borehole information.
Processing array acoustic-logging data to image near-borehole geologic structures
Authors: Tang X. M. , Zheng Y. , Patterson D.
Published: March 2007

Imaging near-borehole structures using acoustic-logging data depends on the data-processing method used. We demonstrate that extracting the up- and downgoing reflections from the data and using those separately for the imaging can significantly improve the image quality. A parametric wave separation is first applied to array data to separate direct and reflection waves. In particular, we use a transmitter array gathered from successive source positions to extract the upgoing reflection. Reflection data can also be enhanced by stacking data along the reflection moveout in array using approximate structural dip information. Implementation of this method to acoustic-logging data processing improves imaging quality, making it possible to image near-borehole geologic structures using conventional array acoustic-logging. A potentially important application of drilling steering is using logging-while-drilling acoustic measurements.
Anisotropic velocity updating for converted-wave prestack time migration
Authors: Miao Xiaogui , Zuk Torre
Published: March 2007

The conventional method used to estimate velocities for converted-wave (C-wave) prestack time migration is awkward because the P-wave velocity [Formula: see text] comes from P-wave processing, the velocity ratio gamma [Formula: see text] is estimated from C-wave data, and the S-wave velocity [Formula: see text] is then derived from [Formula: see text] and gamma. Instead, by using the C-wave velocity [Formula: see text], effective gamma [Formula: see text], and anisotropy parameter [Formula: see text], velocity updating becomes straightforward and more reliable. To update [Formula: see text] for converted-wave time migration, one can carry out hyperbolic moveout analysis on the hyperbolic-moveout-migrated-common-midpoint (HMO-MCMP) gathers. However, the errors in initial [Formula: see text] and anisotropy parameter [Formula: see text] can only be corrected by trial and error. In this article, we propose to remove the effects of initial [Formula: see text] and [Formula: see text] in the HMO-MCMP gathers by inverting the moveout related to the initial [Formula: see text] and [Formula: see text]. This enables a full nonhyperbolic velocity analysis to update not only [Formula: see text] but also [Formula: see text] and [Formula: see text]. To obtain reliable [Formula: see text], we also develop a simultaneous PP/PS anisotropic-parameter estimation method so the [Formula: see text] estimated from P-wave data is compared immediately with the [Formula: see text] derived from [Formula: see text] by using C-wave data. This provides a better constraint for estimating anisotropy parameters. The method has been tested and shows consistent improvement in converted-wave prestack time-migration velocity estimations.
Velocity and resistivity changes during freeze-thaw cycles in Berea sandstone
Authors: Sondergeld Carl H. , Rai Chandra S.
Published: March 2007

We report on simultaneous measurements of resistivity, compressional [Formula: see text], and shear [Formula: see text] velocities made during the temperature cycling of Berea sandstone while at elevated pressure. Temperatures were cycled through the freezing point of the saturating brine. The responses of resistivity and velocities are in phase but are asymmetrical as the brine freezes and thaws. Limited freezing causes no discernible damage to the core. Free water is present below the nominal freezing point of the brine. [Formula: see text], [Formula: see text], and resistivity change by 16%, 24%, and 500%, respectively, over the temperature range of [Formula: see text] at [Formula: see text] confining pressure.
Detecting hydrocarbon reservoirs from CSEM data in complex settings: Application to deepwater Sabah, Malaysia
Authors: Darnet Mathieu , Choo Matthew C. , Plessix René-Edouard , Rosenquist Mark L. , Yip-Cheong Kok , Sims Eldon , Voon John W.
Published: March 2007

Controlled-source electromagnetic (CSEM) field surveys offer a geophysical method to discriminate between high and low hydrocarbon saturations in a potential reservoir. However, the same geological processes that create the possible hydrocarbon reservoir may also create topography and near-surface variations of resistivity (e.g., shallow gas or hydrates) that can complicate the interpretation of CSEM data. In this paper, we discuss the interpretation of such data over a thrust belt prospect in deepwater Sabah, Malaysia. We show that detailed modeling of the key scenarios can help us understand the contributions of topography, near-surface hydrates, and possible hydrocarbons at reservoir depth. Complexity at the surface and at depth requires a 3D electromagnetic modeling code that can handle realistic ten-million-cell models. This has been achieved by using an iterative solver based on a multigrid preconditioner, finite-difference approach with frequency-dependent grid adaptation.
The 4D microgravity method for waterflood surveillance: Part II — Gravity measurements for the Prudhoe Bay reservoir, Alaska
Authors: Ferguson J. F. , Chen T. , Brady J. , Aiken C. L. , Seibert J.
Published: March 2007

Between 1994 and 2002, a series of experiments was conducted at Prudhoe Bay, Alaska, aimed at the development of an effective 4D (or time-lapse) gravity technique. Theoretical investigations had pointed out the potential for monitoring water injection in the [Formula: see text]-deep reservoir, but it was not clear that gravity measurements of sufficient accuracy could be made in the arctic environment. During the course of these experiments, new techniques and instrumentation were introduced and perfected for both gravity and position measurements. Gravity stations are located using high-precision global positioning system (GPS) techniques without permanent monuments. Robust methods for meter drift control have improved noise resistance in relative gravimeter surveys. Absolute gravity measurements with a field-portable instrument maintain absolute gravity levels among surveys. A 4D gravity-difference noise of [Formula: see text] standard deviation has been established at Prudhoe Bay for GPS-controlled relative gravimeter surveys. The lessons learned are now being applied to full-scale waterflood monitoring at Prudhoe Bay. The basic technique is applicable to microgravity surveys and 4D microgravity surveys for any purpose.
Selective-correlation velocity analysis
Authors: Larner Ken , Celis Valmore
Published: March 2007

Increased resolution in computed velocity spectra aids in distinguishing between neighboring primary events from reflectors with conflicting dip and in identifying primaries in the presence of multiples. The transformation from the offset and reflection-time domain to the stacking-velocity and zero-offset-time domain can be achieved using any of several coherence measures based on crosscorrelations among traces in a common-midpoint (CMP) gather or a common-image gather (CIG). Use of just selected subsets of crosscorrelations rather than all possible ones in a gather can improve both the reliability and resolution of velocity analysis. In selective-correlation velocity analysis, we include in the summation only crosscorrelations for those pairs of traces with relative differential moveout of reflections exceeding a chosen threshold value. Comparisons of performance on CMP gathers, both synthetic and field-data, show that selective-correlation velocity analysis considerably enhances the resolving power of velocity spectra over that of conventional crosscorrelation sum (normalized or unnormalized) in the presence of closely interfering reflections, statics distortions, and random noise, at no sacrifice in quality of results, and does so at computational cost comparable to that for conventional velocity analysis.
Rigorous 3D inversion of marine CSEM data based on the integral equation method
Authors: Gribenko Alexander , Zhdanov Michael
Published: March 2007

Marine controlled-source electromagnetic (MCSEM) surveys have become an important part of offshore petroleum exploration. However, due to enormous computational difficulties with full 3D inversion, practical interpretation of MCSEM data is still a very challenging problem. We present a new approach to 3D inversion of MCSEM data based on rigorous integral-equation (IE) forward modeling and a new IE representation of the sensitivity (Fréchet derivative matrix) of observed data to variations in sea-bottom conductivity. We develop a new form of the quasi-analytical approximation for models with variable background conductivity (QAVB) and apply this form for more efficient Fréchet derivative calculations. This approach requires just one forward modeling on every iteration of the regularized gradient-type inversion algorithm, which speeds up the computations significantly. We also use a regularized focusing inversion method, which provides a sharp boundary image of the petroleum reservoir. The methodology is tested on a 3D inversion of the synthetic EM data representing a typical MCSEM survey conducted for offshore petroleum exploration.
Preferred orientation and elastic anisotropy in shales
Authors: Lonardelli Ivan , Wenk Hans-Rudolf , Ren Y.
Published: March 2007

Anisotropy in shales is becoming an important issue in exploration and reservoir geophysics. In this study, the crystallographic preferred orientation of clay platelets that contributes to elastic anisotropy was determined quantitatively by hard monochromatic X-ray synchrotron diffraction in two different shales from drillholes off the coast of Nigeria. To analyze complicated diffraction images with five different phases (illite/smectite, kaolinite, quartz, siderite, feldspar) and many overlapping peaks, we applied a methodology based on the crystallographic Rietveld method. The goal was to describe the intrinsic physical properties of the sample (phase composition, crystallographic preferred orientation, crystal structure, and microstructure) and compute macroscopic elastic properties by averaging single crystal properties over the orientation distribution for each phase. Our results show that elastic anisotropy resulting from crystallographic preferred orientation of the clay particles can be determined quantitatively. This provides a possible way to compare measured seismic anisotropy and texture-derived anisotropy and to estimate the contribution of the low-aspect ratio pores aligned with bedding.
Waveform design for electroseismic exploration
Authors: Hornbostel Scott C. , Thompson A. H.
Published: March 2007

In earlier work, we described field tests that successfully detected electromagnetic-to-seismic (ES) conversions from gas sands and carbonate reservoirs. ES conversion amplitudes measure the electric properties of permeable rock with near-seismic resolution. This information is a new indicator of hydrocarbons. ES conversions produce small seismic responses. Detecting these signals requires high-power electromagnetic sources and high-sensitivity detectors. Extraction of signal from noise also requires sophisticated signal processing. Here, we describe coded waveforms of binary sequences optimized for the expected signals. These coded waveforms distinguish between linear and nonlinear conversions. We detected both linear and nonlinear conversions in field studies. Novel, high-power signal generators synthesize the required sequences from three-phase power lines. The electroseismic exploration system includes optimized source electrodes and digital accelerometers that are free of electromagnetic interference.
Seismic characterization of multiple fracture sets at Rulison Field, Colorado
Authors: Vasconcelos Ivan , Grechka Vladimir
Published: March 2007

Conventional fracture-characterization methods assume the presence of a single set of aligned, vertical cracks in the subsur-face. We relax this assumption and demonstrate the feasibility of seismic characterization of multiple fracture sets. Our technique relies on recent numerical findings indicating that multiple, differently oriented, possibly intersecting planar cracks embedded in an otherwise isotropic host rock result in a nearly orthorhombic (or orthotropic) effective medium. Here, the governing parameters of crack-induced orthotropy are estimated from 3D, wide-azimuth, multicomponent seismic reflection data acquired over the tight-gas Rulison Field in Colorado. We translate strong azimuthal variations of the normal-moveout velocities intointerval crack densities, fracture orientations, type of fluid infill, and velocities of P- and S-waves in an unfractured rock. Our inversion procedure identifies a set of cracks aligned in approximately west northwest-east southeast direction in the western part of the study area and multiple, likely intersecting fractures in its eastern part. We validate both our underlying theoretical model and the obtained estimates by two independent measurements: (1) the estimated fluid-infill parameter indicates dry cracks as expected for the gas-producing sandstones at Rulison; and (2) the obtained crack orientations are supported by well observations. As a by-product of fracture characterization, we build an anisotropic velocity model of the Rulison reservoir which, we believe, is the first orthorhombic velocity field constructed from surface seismic data.
Electromagnetic imaging of a complex ore body: 3D forward modeling, sensitivity tests, and down-mine measurements
Authors: Queralt Pilar , Jones Alan G. , Ledo Juanjo
Published: March 2007

This study investigated the capability of audio-magnetotellurics (AMT) not only to detect, but also to delineate complex conductive ore bodies at minable depths. A detailed 3D numerical-electrical resistivity model of the Bathurst no. 12 deposit (New Brunswick, Canada) was constructed using available geologic and geophysical information. Different geologic and data acquisition conditions were simulated: presence of overburden; different geometries, dimensions, and positions of the ore body; and different data sampling regimes. The behavior of the surface 3D electromagnetic fields was compared with that from bodies of infinite strike extent. The 3D and 2D AMT responses were similar at high frequencies, so 2D modeling was shown to be both valid and sufficient. However, at low frequencies only those responses for current flow perpendicular to the body (the transverse magnetic mode in a 2D case), were reasonably similar. The 2Dinversions showed that the position and the top of the 3D ore body were well resolved, but the bottom of the ore body's resis-tivity were poorly resolved. To increase resolution at depth below ore bodies, and to possibly extend mine life, we recommend that AMT measurements are taken from within mines. Simple mod-els of ore bodies were simulated to show responses at depth, and to undertake body stripping of the overlying structures. The tests showed that conductive structures above the measurement level can have a strong influence on imaging of conducting zones below, and can produce distortion effects in apparent resistivity and phase. Although the body-stripping approach reduces these effects and gives an indication of whether there are conductive structures below, the resulting image is considerably different from that of a model without overlying conductive structures. Full 3D inversion, holding known structures at constant, is required.
Resilience as an Attribute of the Developmental System
Authors: LERNER RICHARD M.
Published: March 2007

Abstract:  When conceptualized within a developmental systems theoretical framework, resilience involves mutually beneficial, reciprocally influential relations between a person and his or her context. The key features of developmental systems theory, which stress the plasticity of these relations, lead to an optimistic view of the possibility of promoting positive human development (PHD) across the life span. The results of recent longitudinal research about adolescent development allow this period to serve as a sample case of how positive development is associated with the alignment of the strengths of individuals with ecological resources for healthy growth.
Promoting Resilience in Children and Youth
Authors: GREENBERG MARK T.
Published: March 2007

Abstract:  Preventive interventions focus on reducing risk and promoting protective factors in the child as well as their cultural ecologies (family, classroom, school, peer groups, neighborhood, etc). By improving competencies in both the child and their contexts many of these interventions promote resilience. Although there are now a substantial number of preventive interventions that reduce problem behaviors and build competencies across childhood and adolescence, there has been little integration with recent findings in neuropsychology and neuroscience. This article focuses on the integration of prevention research and neuroscience in the context of interventions that promote resilience by improving the executive functions (EF); inhibitory control, planning, and problem solving skills, emotional regulation, and attentional capacities of children and youth. Illustrations are drawn from recent randomized controlled trials of the Promoting Alternative Thinking Strategies (PATHS) curriculum. The discussion focuses on the next steps in transdisciplinary research in prevention and social neuroscience.
Behavioral Differences in Aggressive Children Linked with Neural Mechanisms of Emotion Regulation
Authors: LEWIS MARC D. , GRANIC ISABELA , LAMM CONNIE
Published: March 2007

Abstract:  Children with aggressive behavior problems may have difficulties regulating negative emotions, resulting in harmful patterns of interpersonal behavior at home and in the schoolyard. Ventral and dorsal regions of the prefrontal cortex (PFC) have been associated with response inhibition and self‐control—key components of emotion regulation. Our research program aims to explore differences among aggressive and normal children in the activation of these cortical regions during emotional episodes, to the extent possible using electrophysiological techniques, to identify diagnostic subtypes, gain insights into their interpersonal difficulties, and help develop effective treatment strategies. This report reviews several recent studies investigating individual and developmental differences in cortical mechanisms of emotion regulation, corresponding with different patterns of interpersonal behavior. Our methods include event‐related potentials (ERPs) and cortical source modeling, using dense‐array electroencephalography (EEG) technology, as well as videotaped observations of parent–child interactions, with both normal and aggressive children. By relating patterns of brain activation to observed behavioral differences, we find (i) a steady decrease in cortical activation subserving self‐regulation across childhood and adolescence, (ii) different cortical activation patterns as well as behavioral constellations distinguishing subtypes of aggressive children, and (iii) robust correlations between the activation of cortical mediators of emotion regulation and flexibility in parent–child emotional communication in children referred for aggressive behavior problems. These findings point toward models of developmental psychopathology based on the interplay among biological, psychological, and social factors.
A Multiple‐Levels‐of‐Analysis Perspective on Resilience
Authors: CICCHETTI DANTE , BLENDER JENNIFER A.
Published: March 2007

Abstract: Resilient functioning, the attainment of unexpected competence despite significant adversity, is among the most intriguing and adaptive phenomena of human development. Although growing attention has been paid to discovering the processes through which individuals at high risk do not develop maladaptively, the empirical study of resilience has focused predominantly on detecting the psychosocial determinants of the phenomenon. For the field of resilience to grow in ways that are commensurate with the complexity inherent to the construct, efforts to understand underlying processes will be facilitated by the increased implementation of interdisciplinary research designed within a developmental psychopathology framework. Research of this nature would entail a consideration of psychological, biological, and environmental–contextual processes from which pathways to resilience might eventuate (known as equifinality), as well as those that result in diverse outcomes among individuals who have achieved resilient functioning (know as multifinality). The possible relation between the mechanisms of neural plasticity and resilience and specific suggestions concerning research questions needed to examine this association are discussed. Examples from developmental neuroscience and molecular genetics are provided to illustrate the potential of incorporating biology into the study of resilience. The importance of adopting a multiple‐levels‐of‐analysis perspective for designing and evaluating interventions aimed at fostering resilient outcomes in persons facing significant adversity is emphasized.
Evolutionary Basis of Adaptation in Resilience and Vulnerability
Authors: HOFER MYRON A.
Published: March 2007

Abstract:  This masterful and wide‐ranging paper gives us a clear picture of the need for interdisciplinary studies of resilience and vulnerability. We need to go beyond the interacting events at the different levels to see clearly that multiple levels of analysis and concept do not themselves interact, but instead give us different aspects of a biological, psychological, or behavioral event. Thus, no levels are reducible to any of the others. In the rest of my discussion, I raise the likelihood that the multiple level responses of “resilience” are no more adaptive in their evolutionary history than the very different responses we call “vulnerability.” Keeping in mind the evolved functions of these responses, and the circumstances of their selection during evolution, will provide us with new ideas and approaches for understanding and intervention.
Emotional Resilience in Early Childhood
Authors: CONWAY ANNE M. , McDONOUGH SUSAN C.
Published: March 2007

Abstract:  To test whether the development of emotional resilience is a function of sensitive caregiving and child negative affect, we tested the joint contributions of 7‐month maternal sensitivity and infant negative affect to the prediction of 33‐month emotional resilience across the first 3 years of life. The aims of this study were to examine whether maternal sensitivity and infant negative affect predict long‐term emotional resilience and whether this was associated with preschool behavior problems. Using a sample of 181 mother–infant dyads, we found that (a) maternal sensitivity at 7 months, but not infant negative affect, longitudinally predicted emotional resilience during preschool and (b) emotional resilience was negatively associated with anxiety/depression in preschool.
Infant Resilience to the Stress of the Still‐Face
Authors: HAM JACOB , TRONICK ED
Published: March 2007

Abstract:  Respiratory sinus arrhythmia (RSA) is related to infant emotion regulation and resilience. However, few studies have examined RSA of infants and mothers during a stressful experience. Even fewer studies have measured infant and mother skin conductance (SC), which in part reflects anxiety. This pilot study examined RSA, heart rate (HR), and SC patterns of 12 five‐month‐old infants and their mothers during normal interaction and a stressful perturbation of the interaction in which the mother does not respond to her infant—the Face‐to‐Face Still‐Face (FFSF) paradigm. Dyads were grouped into four categories by two conditions: whether the infant protested to the Still‐Face episode (SF) and whether they “recovered” from the SF by reducing protest when the mother resumed interaction in the Reunion (RE). Infants who recovered from the SF had the largest increase in RSA from SF to RE. Mothers of infants who recovered from the SF showed a decrease in RSA during the RE, suggesting mobilization of infant soothing behaviors. Mothers of infants who did not recover from the SF showed physiologic markers of anxiety in the form of continued increases in RSA and high levels of SC. Furthermore, these mothers behaved in a manner that was not responsive to their infant's disengagement cues. These pilot results demonstrate the feasibility of measuring infant SC, a measure long disregarded in infant research. The findings suggest that maternal psychophysiology may be related to infant resilience and suggest a bidirectional effect of maternal and infant reactivity.
Pathways of Adaptation from Adolescence to Young Adulthood
Authors: OBRADOVIĆ JELENA , BURT KEITH B. , MASTEN ANN S.
Published: March 2007

Abstract:  This study examines longitudinal change using a person‐centered approach to differentiate patterns of adaptive functioning from adolescence to adulthood. Data are drawn from a 20‐year longitudinal study of competence and resilience in the lives of 205 school children (29% minority). Results indicate five distinct pathways of adaptation: (1) low‐declining, (2) low‐improving, (3) middle‐improving, (4) middle‐declining, and (5) consistently high. The study also compares the five groups on childhood risks and resources, and on longitudinal assessment of competence and adversity. Interestingly, the most dramatic changes in pathways of adaptation occur during the period of emerging adulthood.
Relational and Academic Components of Resilience in Maltreated Adolescents
Authors: RAJENDRAN KHUSHMAND , VIDEKA LYNN
Published: March 2007

Abstract:  This study examines the components of resilience in adolescents (aged 11–15 years; n= 816) who were referred to the child welfare system for maltreatment. Data from a national probability study of children and families in the child welfare system showed that adolescents faced a number of risk factors like maltreatment, poverty, and exposure to violence in the community. Social competence, academic achievement, and a sense of relatedness to caregiver were fit in a structural equation model as components of latent resilience. Social competence and the quality of relationship with a caregiver were strongly linked to latent resilience.
Neighborhood Risk and the Development of Resilience
Authors: VANDERBILT‐ADRIANCE ELLA , SHAW DANIEL S.
Published: March 2007

Abstract:  The purpose of the study was to advance our understanding of resilience by studying multiple protective factors associated with positive adjustment among an ethnically diverse sample of 310 low‐income boys followed prospectively from ages 1.5 to 12 years, using neighborhood quality to define risk status. The results indicated that child and family protective factors measured in early childhood were all significantly associated with positive adjustment at 11 and 12 years of age. However, these results were qualified by risk level, such that parent–child relationship quality was only significantly related to positive outcomes in the context of low levels of risk.
Foxe view of lens development and disease
Authors: Medina-Martinez Olga , Jamrich Milan
Published: March 2007

The recent identification of a mutation in Foxe3 that causes congenital primary aphakia in humans marks an important milestone. Congenital primary aphakia is a rare developmental disease in which the lens does not form. Previously, Foxe3 had been shown to play a crucial role in vertebrate lens formation and this gene is one of the earliest integrators of several signaling pathways that cooperate to form a lens. In this review, we highlight recent advances that have led to a better understanding of the developmental processes and gene regulatory networks involved in lens development and disease.
Ephrin-Eph signalling drives the asymmetric division of notochord/neural precursors inCionaembryos
Authors: Picco Vincent , Hudson Clare , Yasuo Hitoyoshi
Published: March 2007

Asymmetric cell divisions produce two sibling cells with distinct fates,providing an important means of generating cell diversity in developing embryos. Many examples of such cell divisions have been described, but so far only a limited number of the underlying mechanisms have been elucidated. Here,we have uncovered a novel mechanism controlling an asymmetric cell division in the ascidian embryo. This division produces one notochord and one neural precursor. Differential activation of extracellular-signal-regulated kinase(ERK) between the sibling cells determines their distinct fates, with ERK activation promoting notochord fate. We first demonstrate that the segregation of notochord and neural fates is an autonomous property of the mother cell and that the mother cell acquires this functional polarity via interactions with neighbouring ectoderm precursors. We show that these cellular interactions are mediated by the ephrin-Eph signalling system, previously implicated in controlling cell movement and adhesion. Disruption of contacts with the signalling cells or inhibition of the ephrin-Eph signal results in the symmetric division of the mother cell, generating two notochord precursors. Finally, we demonstrate that the ephrin-Eph signal acts via attenuation of ERK activation in the neural-fated daughter cell. We propose a model whereby directional ephrin-Eph signals functionally polarise the notochord/neural mother cell, leading to asymmetric modulation of the FGF-Ras-ERK pathway between the daughter cells and, thus, to their differential fate specification.
StonewallingDrosophilastem cell differentiation by epigenetic controls
Authors: Maines Jean Z. , Park Joseph K. , Williams Meredith , McKearin Dennis M.
Published: March 2007

During Drosophila oogenesis, germline stem cell (GSC) identity is maintained largely by preventing the expression of factors that promote differentiation. This is accomplished via the activity of several genes acting either in the GSC or in its niche. The translational repressors Nanos and Pumilio act in GSCs to prevent differentiation, probably by inhibiting the translation of early differentiation factors, whereas niche signals prevent differentiation by silencing transcription of the differentiation factor Bam. We have found that the DNA-associated protein Stonewall (Stwl) is also required for GSC maintenance. stwl is required cell-autonomously;clones of stwl- germ cells were lost by differentiation,and ectopic Stwl caused an expansion of GSCs. stwl mutants acted as Suppressors of variegation, indicating that stwl normally acts in chromatin-dependent gene repression. In contrast to several previously described GSC maintenance factors, Stwl probably functions epigenetically to prevent GSC differentiation. Stwl-dependent transcriptional repression does not target bam, but rather Stwl represses the expression of many genes, including those that may be targeted by Nanos and Pumilio translational inhibition.
Spontaneous comparisons with others in gay men's judgements of HIV risk
Authors: Gold R S
Published: March 2007

In studies on ‘unrealistic optimism’ (UO), when people are asked questions designed to make them compare their risk of experiencing an undesirable event with that of the average person, they tend to respond that their risk is lower. This study investigated whether comparisons of own and others’ risk also occur spontaneously, unprovoked by such questions. Gay men uninfected with HIV (n = 50) were asked to think aloud about their risk of becoming infected; their comments were audiotaped and analysed. Over half the men added comments relating to others’ risk. The phrasing of these comments and the reported basis for them are described. The men represented others’ risk as relatively high, own risk as relatively low. In the case of one-third of the men, it seemed possible to be confident that a comparison was being made. The findings suggest that comparisons of own and others’ risk do occur spontaneously and that, while the judgements made in UO studies do not capture all the characteristics of those made spontaneously, they resemble them in important ways.
Incidence and prevalence of the metabolic syndrome in a cohort of naive HIV-infected patients: Prospective analysis at 48 weeks of highly active antiretroviral therapy
Authors: Palacios R , Santos J , González M , Ruiz J , Márquez M
Published: March 2007

We undertook a prospective study to assess the prevalence of the metabolic syndrome (MetS) in HIV patients at the start of highly active antiretroviral therapy (HAART), and at 48 weeks, and we also studied its relationship with high-sensitivity C-reactive protein (hs-CRP) in 60 HIV patients who maintained the same regimen during follow-up. The prevalence of MetS rose from 16.6% at baseline to 25% at 48 weeks (P = 0.0001). During follow up, 7/50 patients developed MetS, leading an incidence of 14/100 patients/year. The MetS was associated with age, homosexuality, and lower hepatitis C virus prevalence; only age remained significant in the multivariate analysis (for each five-year increase: β coefficient 4.26, 95% confidence interval, 3.80-4.75; P = 0.0039). The hs CRP values were similar in patients with and without the MetS, and they did not increase at 48 weeks of HAART
Prevalence of bacterial vaginosis among young women in low-income populations of coastal Peru
Authors:   NIMH Collaborative HIV/STI Prevention Trial Group, Jones F R , Miller G , Gadea N , Meza R , Leon S , Perez J , Lescano A G , Pajuelo J , Caceres C F , Klausner J D , Coates T J
Published: March 2007

The goal of this study was to determine the prevalence of bacterial vaginosis (BV) in Peruvian women from socioeconomically deprived populations and to determine the association between BV and risk factors for sexually transmitted diseases (STDs). Women were administered an epidemiologic survey to determine sexual risk behaviour and they provided biological samples to test for BV and STDs. The prevalence of BV was high (27%) and was significantly associated with having a bacterial STD or trichomoniasis. Age, marital status, and a history of sex work, but not of sexual experience, frequency of intercourse, and unprotected intercourse, were associated with BV. As BV may be a marker for STDs, screening for STDs should be performed in individuals with BV to promote early detection and treatment of co-infecting sexually transmitted pathogens.
Usage of stavudine (D4T) – a retrospective analysis in a South London hospital
Authors: Lechelt Martin , Mccormick Steve , De Ruiter Annemiek
Published: March 2007

British HIV Association (BHIVA) guidelines are updated on a regular basis with emergence of new clinical evidence. In June 2003, the BHIVA guidelines recommended that stavudine (D4T)-containing regimens are less preferred if other viable options are available. A retrospective analysis was conducted to establish whether local prescribing practice reflects national guidance offered by BHIVA. This study identifies 28 patients on D4Tcombinations, which represents 2% of the total treated group in our clinic population. In all, 89% (25/28) of patients had a viral load of <50 copies/mL and CD4 counts ranged from 122 to 1016 cells/mm3. In this study, 12/28 patients had documented lipodystrophy. Seventeen out of 28 patients had no clear documented reasons for remaining on D4T, eight patients preferred to continue and three patients continued because of genotypic findings. This study shows that a small proportion of patients are still on D4T-containing regimen for the following reason –patient's choice, side-effects, toxicities and interaction. The majority of patients remaining on D4T had documented lipodystrophy changes. Therefore, clinicians continuing to prescribe D4T should document the precise reason for its continued use. If patients prefer to continue D4T, this should be well documented to circumvent any medicolegal consequences, should toxicity develop later.
Increased exposure to hepatitis B virus infection in HIV-positive South African antenatal women
Authors: Burnett R J , Ngobeni J M , François G , Hoosen A A , Leroux-Roels G , Meheus A , Mphahlele M J
Published: March 2007

The prevalence of markers for hepatitis B virus (HBV) exposure and active infection in HIV-positive (n = 710) and HIV-negative (n = 710) pregnant South African women was investigated. The following statistically significant increases in the HIV-positive group were found: anti-hepatitis B core antigen (anti-HBc) (37.3% versus 28.6%; odds ratio [OR]: 1.49); anti-hepatitis B surface antigen (anti-HBs) (29.5% versus 20.1%; OR: 1.66); exposure based on hepatitis B surface antigen (HBsAg) and anti-HBc (39.2% versus 30.1 %; OR: 1.49); and exposure based on anti-HBs, anti-HBc and HBsAg (37.1% versus 24.5%; OR: 1.82). However, there was no increase in active HBV infections, with 2.4% of the HIV positives and 2.2% of the HIV negatives being HBV DNA positive. Although the impact that HIV has had on the prevalence of HBV in this population group is not as pronounced as that found in areas of low endemicity (where up to seven-fold increases have been reported), there is a statistically significant increased exposure to HBV.
Pad – a new self-collection device for human papillomavirus
Authors: Kim S R , Song S Y , Kim D S , Lee J-W , Kim B-G , Bae D-S , Song E S , Joo H J
Published: March 2007

This study was designed to determine the accuracy and agreement of a self-collection method using pad for human papillomavirus (HPV) DNA. One hundred and thirty-four patients at university hospitals voluntarily participated in the accuracy study, and 314 volunteers participated in the agreement study at local clinics. DNA was extracted and amplified using HPV L1 consensus primers designed for the direct sequencing. In the accuracy study, all samples were probed via histological examinations. With regard to the detection of squamous intraepithelial lesion (SIL), self-collection pad sampling displays sensitivity, of 76.9%, and specificity, of 93.3%. Three hundred and fourteen self-collection pad samples and the concurrent physicians’ samples showed a 97.8% agreement, with a Kappa value of 0.9200. A new self-collection pad for the detection of HPV DNA appears to constitute an easy, rapid, and convenient alternative method for the cervical cancer screening of many women with the virtue of being incredibly readily accessible.
Acts of cultural identification: Tim O'Brien's July, July
Authors: Stocks Claire
Published: March 2007

In a 1994 interview, Tim O'Brien insists that one of the key aims of his fiction is to invite the reader to occupy the position of the author/narrator so that the reader is encouraged, as O'Brien puts it, to identify with the experience which is being narrated. O'Brien's desire to enable
the presumably non-traumatized reader to occupy the position of the traumatized writer/narrator demonstrates his concern with attempting to find ways of overcoming the division between those who experienced the war in Vietnam and those who did not. In this paper I argue that O'Brien's most
recent novel, July, July (2002) constitutes his most sustained investigation of this theme. O'Brien attempts to negotiate the extremes of individualisation and universalisation appealed to in writing about war, and in writing about trauma more generally by situating the trauma of Vietnam,
not within the geographical confines of South East Asia, but within the specific temporal confines of the late 1960s and early 1970s. I employ theories of hysteria developed by Juliet Mitchell and theories of mourning proposed by Nicholas Abraham and Maria Torok to investigate how loss is
experienced by the class of 69. Furthermore, I explore how, by emphasising cultural or historical, rather than the psychological, equivalence between survivors of trauma, O'Brien is able to probe the limits of trauma as it is generally defined by canonical trauma writers including Judith Herman
and Kal Tal. In July, July O'Brien creates a group of literal and metaphorical amputees who have all been similarly wounded by their shared time and place in history. In doing this, O'Brien extends the relevance and applicability of the experience of trauma to those who did not participate
directly in the war, while still resisting the urge to universalize or suggest that trauma is equally accessible to all subjects. O'Brien's work in this area seems timely and suggests that, in the light of recent events like America's wars in the Gulf, 9/11 and the War on Terror' which challenge
the polarisation between traumatized survivor and generally non-traumatized population, new interpretations of what it means to be traumatized are required.
Storytelling and cultural identity: Louise Erdrich's exploration of the German/American connection in The Master Butchers Singing Club
Authors: Lischke Ute , McNab David T
Published: March 2007

To understand stories, one must understand the spirit of the stories and the spirit of the person and the family who is telling them. Above all, one must know oneself. For Louise Erdrich, the American writer of Mtis/Cree/Chippewa (also known as Anishinabe or Ojibwa) origin on her mother's
side and German/ Jewish/Catholic heritage, on her father's side, this has meant a lifelong commitment to writing in order to maintain a sense of sanity and stability. For it is this mixed identity that continually confronts her with a sense of, as she describes it, unziemliches Verlangen,
unseemly longing. Erdrich writes about the interaction between Natives and Europeans in her novels and as writer and storyteller she incorporates not one, but several cultural identities. In much of the research about Erdrich these German/American connections have been all but ignored. This
article seeks to address that anomaly.
No place like home? Or impossible homecomings in the films of Fatih Akin
Authors: Berghahn Daniela
Published: March 2007

Fatih Akin, one of the most prominent directors of contemporary German-Turkish cinema, describes himself as a German filmmaker and at least until the international success ofGegen die Wand/Head-On(2004) downplayed the relevance of his ethnic background for his creative career. And yet, his feature films exhibit most of the characteristics associated with accented cinema, a type of cinema which has been identified by Hamid Naficy as an aesthetic response to displacement through exile, migration or diaspora. The underlying theme of Akin's films is the migrant's experience of rootlessness and the redemptive promise inherent in the return to onesHeimat. This paper examines chronotopes of homeland inKurz und schmerzlos/Short Sharp Shock(1998),Solino(2002) andHead-Onand asks to what extent the preoccupation withHeimat, alongside the eclectic mix of generic templates which have informed Akin's films, underscore the cultural hybridity of hisoeuvre.
Trendsetting and product placement in Bollywood film: Consumerism through consumption
Authors: Kripalani Coonoor
Published: March 2007

This paper looks at the relatively new practice of in-film advertizing in popular Hindi films. Acknowledging the impact of popular films and iconic stars since the 1940s and 50s on styles, trends and ideology, the paper explores how this powerful medium is now being used for product
placement and brand endorsement in India. Appealing to the rising affluence of Indian audiences, branded goods are most likely to appear in films such as high-end luxury consumer goods like mobile phones, cars and motorcycles. Realizing the potential of celebrity endorsements and the advantages
of in-film placements, the advertizing industry views movies as the optimum medium for building brands. Equally, the film industry is happy to accommodate in-film advertizing as it serves to defray production costs, as well as the costs of marketing and promoting films. This trend, which is
likely to grow, encourages consumerism through consumption in a growing market economy.