bluuebunny/crossref_metadata_2025 huggingface dataset:
Parenting With Mild Intellectual Deficits: Parental Expectations and the Educational Attainment of Their Children
Authors: Taylor Julie Lounds , Hurd Heather Doescher , Seltzer Marsha Mailick , Greenberg Jan S. , Floyd Frank J.
Published: June 2010

We examined how the educational expectations that parents with mild intellectual deficits had for their children shaped their children's attainment, and how parents' own intellectual limitations affected this process. We identified 612 parents with mild intellectual deficits and 2,712 comparison parents from the Wisconsin Longitudinal Study, a prospective longitudinal study in which participants were followed from ages 18 to 64. Compared to the norm, parents with mild intellectual deficits expected their children to complete less education, even after controlling for sociodemographic background variables, and children of parents with mild intellectual deficits did, in fact, complete fewer years of education. For both groups, parental expectations were the strongest predictor of attainment. Results suggest that disparities in education are shaped in part by parents' beliefs about educational opportunities.
Electromagnetic enhancement by a single nano-groove in metallic substrate
Authors: Zhang Siwen , Liu Haitao , Mu Guoguang
Published: June 2010

We propose systematic investigations of the electromagnetic enhancement by a single nano-groove in gold substrate. The impacts of the groove parameters and of the illumination conditions on the enhanced intensity are explored using a fully vectorial numerical method. The obtained data can be well predicted and explained by a simple Fabry–Perot model. By virtue of the semi-analytical model, we identify two main factors that enable giant electric-field enhancement in very narrow grooves: the Fabry–Perot resonance and the large wave impedance of the fundamental mode in the groove.
Wavelength adjustment using an eye model from aberrometry data
Authors: Nam Jayoung , Rubinstein Jacob , Thibos Larry
Published: June 2010

We developed a method to convert aberrometry data obtained in one wavelength to the corresponding data in another wavelength using an eye model. A single map of aberrometry data is used to construct a free-form one-surface eye model. A general algorithm for the surface construction is described and implemented for real aberrometry data. Our method can handle varying conjugate distances of the measurement plane of the aberrometer and can also manage the chief ray prism that may be present. The algorithm is validated with the aid of an artificial plastic eye. The wavefronts in different wavelengths are compared through the Zernike analysis not only for lower-order aberrations, but also for higher-order aberrations. The results show that the changes of the Zernike aberration coefficients due to wavelengths are non-uniform. The defocus term has the highest effect from wavelength changes, which is consistent with the previous literature. Our method is compared with two approximate semi-analytical algorithms. The wavelength adjustments from a multi-surface eye model are contrasted with our method. We prove analytically that the conventional method of wavelength adjustment is based on paraxial analysis. In addition, we provide a method of finding the chief ray using back-projection in some cases and discuss different meanings of prism.
One step back
Authors: Lamond Ian
Published: June 2010

From 2005 to 2006 LUDUS Dance, a professional contemporary dance and dance-in-education company based in the English city of Lancaster were funded by the Arts Council England to deliver a dance programme to a school for children encountering profound and multiple learning difficulties
(PMLD). Following the reported impact of incorporating dance into the educational experience of the participating children, this article considers why dance and somatic practice may be of particular significance for the individual encountering PMLD, situating the question of the place of dance
and movement in education, and its impact on those encountering PMLD, in a deeper theoretical context.
The symbiogenic experience: towards a framework for understanding humanmachine coupling in the interactive arts
Authors: Castellanos Carlos , Gromala Diane
Published: June 2010

This article outlines a research agenda that addresses the question of how contemporary interactive arts practice can evolve new strategies or ways of facilitating the development and representation of subjective experiences that induce an embodied felt sense of the humanmachine co-evolution. To help answer this question, the term symbiogenic has been created as a shorthand or umbrella term to better discuss these types of experiences and the concepts they introduce. The term symbiogenic is taken from symbiogenesis, the evolutionary theory introduced in 1909 by Russian biologist Konstantin Mereschkowsky and expanded in the modern era by Dr. Lynn Margulis (1993, 1981). This theory emphasizes cooperation and other more complex interactions between organisms that go beyond mere competition. The research starts from the conception that there currently exists a range of interactive artworks that examine and engage with the increasing cooperation and co-evolution that humans are experiencing with their technological environment. However, what is proposed is that interactive or technological art can go further and provoke a bodily felt sense of this dynamic and thus bring into greater consciousness the co-dependent and co-evolutionary path of our relationship with technology. It is believed that these experiences can be both developed and identified within an artistic context but they lack a cohesive conceptual framework from which to study and analyse them.
Evolutionary aesthetics: rethinking the role of function in art and design
Authors: Coulter-Smith Graham
Published: June 2010

In the first half of the twentieth century there was a remarkable convergence of art and design in De Stijl, Constructivism and the Bauhaus. But in the second half of the twentieth century fine art relinquished its liaison with design due to the influence of Dada and Surrealism's postromantic
antagonism to practical-functionalism. Dada and Surrealism and postmodern fine art are characterized by a critique of the dominant social discourse of functionalism and the demand for a sublime poetics to be brought into everyday life. This article argues that the apparent antipathy between
postmodern fine art and design can be ameliorated if we critically analyse interpretations of evolutionary theory by postromantic philosophers such as Nietzsche, Bergson, and Deleuze and Guattari. When Bergson notes that practical-functional reasoning was created by evolution he reveals a
flaw in the pursuit of an aesthetics that is totally opposed to commonsense and practical-functionalism. And when we turn to Deleuze and Guattari we find another valuable concept in the form of their notion of the machinic, which assists further in reconciling the postromantic emphasis on
the sublime with the practicality of mechanism. Moreover, Deleuze and Guattari's notion of the machinic is informed by chaos theory, which allows further elaboration in terms of complexity theory. Complexity theory can be understood as a process philosophy that has no need to figure the sublime
in terms of a mysterious force of nature because the mystery is located within complex interactions among a manifold of components, what one might refer to as a cosmic, machinic, combinatoire that arises out of what Christopher Langton has called the edge of chaos. This makes it possible to
replace the emphasis on desire as the fundamental force of nature evident in Nietzsche, Bergson, Deleuze and Guattari with a complexity-theoretical concept of a cosmicmachinic combinatoire. It is then possible to formulate a machinic, evolutionary aesthetics that can reconcile the postromantic
demand for sublimity with the demand for practical-functionalism that lies at the heart of the discipline of design. In place of the modernist machine aesthetic that informed De Stijl, Constructivism and the Bauhaus we would have a postmodernist machinic aesthetic.
Designing the art of attention
Authors: Levy Ellen K
Published: June 2010

The author analyses the design of her collaborative animation about inattention blindness, the phenomenon of not being able to see things that are actually there, and compares it to related scientific research.1 The term was coined by Arien Mack and Irvin Rock in 1992. Stealing
Attention, co-created by the author and neuroscientist Michael E. Goldberg, Director of the Mahoney Center for Brain and Behavior at Columbia University, explored inattention blindness. Animated images of hands playing the con game Three-Card Monte were superimposed over images of antiquities
stolen from Iraq. The flashing cards, yellow circles and stated instructions distracted the viewer from seeing the images of stolen antiquities, which disappeared from depicted shelves one by one over the time span of approximately three minutes. The author considers five questions: What is
perceived without attention What does attention select Under what circumstances can attention be shifted Is an observer trained in art less likely to be distracted Can attention be trained
Synaptic and Vesicular Coexistence of VGLUT and VGAT in Selected Excitatory and Inhibitory Synapses
Authors: Zander Johannes-Friedrich , Münster-Wandowski Agnieszka , Brunk Irene , Pahner Ingrid , Gómez-Lira Gisela , Heinemann Uwe , Gutiérrez Rafael , Laube Gregor , Ahnert-Hilger Gudrun
Published: June 2010

The segregation between vesicular glutamate and GABA storage and release forms the molecular foundation between excitatory and inhibitory neurons and guarantees the precise function of neuronal networks. Using immunoisolation of synaptic vesicles, we now show that VGLUT2 and VGAT, and also VGLUT1 and VGLUT2, coexist in a sizeable pool of vesicles. VGAT immunoisolates transport glutamate in addition to GABA. Furthermore, VGLUT activity enhances uptake of GABA and monoamines. Postembedding immunogold double labeling revealed that VGLUT1, VGLUT2, and VGAT coexist in mossy fiber terminals of the hippocampal CA3 area. Similarly, cerebellar mossy fiber terminals harbor VGLUT1, VGLUT2, and VGAT, while parallel and climbing fiber terminals exclusively contain VGLUT1 or VGLUT2, respectively. VGLUT2 was also observed in cerebellar GABAergic basket cells terminals. We conclude that the synaptic coexistence of vesicular glutamate and GABA transporters allows for corelease of both glutamate and GABA from selected nerve terminals, which may prevent systemic overexcitability by downregulating synaptic activity. Furthermore, our data suggest that VGLUT enhances transmitter storage in nonglutamatergic neurons. Thus, synaptic and vesicular coexistence of VGLUT and VGAT is more widespread than previously anticipated, putatively influencing fine-tuning and control of synaptic plasticity.
Motor Sequences and the Basal Ganglia: Kinematics, Not Habits
Authors: Desmurget Michel , Turner Robert S.
Published: June 2010

Despite a lack of definitive evidence, it is frequently proposed that the basal ganglia (BG) motor circuit plays a critical role in the storage and execution of movement sequences (or motor habits). To test this hypothesis directly, we inactivated the sensorimotor territory of the globus pallidus internus (sGPi, the main BG motor output) in two monkeys trained to perform overlearned and random sequences of four out-and-back reaching movements directed to visual targets. Infusion of muscimol (a GABAAagonist) into sGPi caused dysmetria and slowing of individual movements, but these impairments were virtually identical for overlearned and random sequences. The fluid predictive execution of learned sequences and the animals' tendency to reproduce the sequence pattern in random trials was preserved following pallidal blockade. These results suggest that the BG motor circuit contributes to motor execution, but not to motor sequencing or the storage of overlearned serial skills.
Postdepolarization Potentiation of GABAAReceptors: A Novel Mechanism Regulating Tonic Conductance in Hippocampal Neurons
Authors: Ransom Christopher B. , Wu Yuanming , Richerson George B.
Published: June 2010

Ambient GABA in the brain activates GABAAreceptors to produce tonic inhibition. Membrane potential influences both GABA transport and GABAAreceptors and could thereby regulate tonic inhibition. We investigated the voltage dependence of tonic currents in cultured rat hippocampal neurons using patch-clamp techniques. Tonic GABAAconductance increased with depolarization from 15 ± 3 pS/pF at −80 mV to 29 ± 5 pS/pF at −40 mV. Inhibition of vesicular or nonvesicular GABA release did not prevent voltage-dependent increases of tonic conductance. Currents evoked with exogenous GABA (1 μm) were outwardly rectifying, similar to tonic currents caused by endogenous GABA. These results indicate that the voltage-dependent increase of tonic conductance was attributable to intrinsic GABAAreceptor properties rather than an elevation of ambient GABA. After transient depolarization to +40 mV, endogenous tonic currents measured at −60 mV were increased by 75 ± 17%. This novel form of tonic current modulation, termed postdepolarization potentiation (PDP), recovered with a time constant of 63 s, was increased by exogenous GABA and inhibited by GABAAreceptor antagonists. Measurements ofEGABAshowed PDP was caused by increased conductance and not a change in the anion gradient. To assess the functional significance of PDP, we used voltage-clamp waveforms that replicated epileptiform activity. PDP was produced by this pathophysiological depolarization. These data show that depolarization produces prolonged potentiation of tonic conductance attributable to voltage-dependent properties of GABAAreceptors. These properties are well suited to limit excitability during pathophysiological depolarization accompanied by rises in ambient GABA, such as occur during seizures and ischemia.
MicroRNA-Deficient Schwann Cells Display Congenital Hypomyelination
Authors: Yun Beth , Anderegg Angela , Menichella Daniela , Wrabetz Lawrence , Feltri M. Laura , Awatramani Rajeshwar
Published: June 2010

MicroRNAs, by modulating gene expression, have been implicated as regulators of various cellular and physiological processes, including differentiation, proliferation, and cancer. Here, we study the role of microRNAs in Schwann cell (SC) differentiation by conditional removal of the microRNA processing enzyme Dicer1. We reveal that both male and female mice lackingDicer1in SC (Dicer1conditional knock-outs) display a severe neurological phenotype resembling congenital hypomyelination. Ultrastructural analyses show that many SC lackingDicer1are stalled in differentiation at the promyelinating state and fail to myelinate axons. Gene expression analyses reveal a failure to extinguish genes characteristic of the undifferentiated state such asSox2,Jun, andCcnd1. Sox2 and Jun are well characterized negative regulators of SC differentiation. Consistent withSox2/Junmaintenance,Egr2, a master regulator of the myelinating program, is drastically downregulated and likely accounts for the myelination defect. We posit a model wherein microRNAs are critical for downregulation of antecedent programs of gene expression. In SC differentiation, this is particularly relevant in the key developmental transition from a promyelinating to myelinating SC.
Interhemispheric Regulation of the Medial Prefrontal Cortical Glutamate Stress Response in Rats
Authors: Lupinsky Derek , Moquin Luc , Gratton Alain
Published: June 2010

While stressors are known to increase medial prefrontal cortex (PFC) glutamate (GLU) levels, the mechanism(s) subserving this response remain to be elucidated. We used microdialysis and local drug applications to investigate, in male Long–Evans rats, whether the PFC GLU stress response might reflect increased interhemispheric communication by callosal projection neurons. We report here that tail-pinch stress (20 min) elicited comparable increases in GLU in the left and right PFC that were sodium and calcium dependent and insensitive to local glial cystine–GLU exchanger blockade. Unilateral ibotenate-induced PFC lesions abolished the GLU stress response in the opposite hemisphere, as did contralateral mGlu2/3receptor activation. Local dopamine (DA) D1receptor blockade in the left PFC potently enhanced the right PFC GLU stress response, whereas the same treatment applied to the right PFC had a much weaker effect on the left PFC GLU response. Finally, the PFC GLU stress response was attenuated and potentiated, respectively, following α1-adrenoreceptor blockade and GABABreceptor activation in the opposite hemisphere. These findings indicate that the PFC GLU stress response reflects, at least in part, activation of callosal neurons located in the opposite hemisphere and that stress-induced activation of these neurons is regulated by GLU-, DA-, norepinephrine-, and GABA-sensitive mechanisms. In the case of DA, this control is asymmetrical, with a marked regulatory bias of the left PFC DA input over the right PFC GLU stress response. Together, these findings suggest that callosal neurons and their afferentation play an important role in the hemispheric specialization of PFC-mediated responses to stressors.
Reduced Cortical BDNF Expression and Aberrant Memory inCarfKnock-Out Mice
Authors: McDowell Kelli A. , Hutchinson Ashley N. , Wong-Goodrich Sarah J.E. , Presby Matthew M. , Su Dan , Rodriguiz Ramona M. , Law Krystal C. , Williams Christina L. , Wetsel William C. , West Anne E.
Published: June 2010

Transcription factors are a key point of convergence between the cell-intrinsic and extracellular signals that guide synaptic development and brain plasticity. Calcium-response factor (CaRF) is a unique transcription factor first identified as a binding protein for a calcium-response element in the gene encoding brain-derived neurotrophic factor (Bdnf). We have now generatedCarfknock-out (KO) mice to characterize the function of this factorin vivo. Intriguingly,CarfKO mice have selectively reduced expression ofBdnfexon IV-containing mRNA transcripts and BDNF protein in the cerebral cortex, whereas BDNF levels in the hippocampus and striatum remain unchanged, implicating CaRF as a brain region-selective regulator of BDNF expression. At the cellular level,CarfKO mice show altered expression of GABAergic proteins at striatal synapses, raising the possibility that CaRF may contribute to aspects of inhibitory synapse development.CarfKO mice show normal spatial learning in the Morris water maze and normal context-dependent fear conditioning. However they have an enhanced ability to find a new platform location on the first day of reversal training in the water maze and they extinguish conditioned fear more slowly than their wild-type littermates. Finally,CarfKO mice show normal short-term (STM) and long-term memory (LTM) in a novel object recognition task, but exhibit impairments during the remote memory phase of testing. Together, these data reveal novel roles for CaRF in the organization and/or function of neural circuits that underlie essential aspects of learning and memory.
Prefrontal Cortex Fails to Learn from Reward Prediction Errors in Alcohol Dependence
Authors: Park Soyoung Q. , Kahnt Thorsten , Beck Anne , Cohen Michael X , Dolan Raymond J. , Wrase Jana , Heinz Andreas
Published: June 2010

Patients suffering from addiction persist in consuming substances of abuse, despite negative consequences or absence of positive consequences. One potential explanation is that these patients are impaired at flexibly adapting their behavior to changes in reward contingencies. A key aspect of adaptive decision-making involves updating the value of behavioral options. This is thought to be mediated via a teaching signal expressed as a reward prediction error (PE) in the striatum. However, to exert control over adaptive behavior, value signals need to be broadcast to higher executive regions, such as prefrontal cortex. Here we used functional MRI and a reinforcement learning task to investigate the neural mechanisms underlying maladaptive behavior in human male alcohol-dependent patients. We show that in alcohol-dependent patients the expression of striatal PEs is intact. However, abnormal functional connectivity between striatum and dorsolateral prefrontal cortex (dlPFC) predicted impairments in learning and the magnitude of alcohol craving. These results are in line with reports of dlPFC structural abnormalities in substance dependence and highlight the importance of frontostriatal connectivity in addiction, and its pivotal role in adaptive updating of action values and behavioral regulation. Furthermore, they extend the scope of neurobiological deficits underlying addiction beyond the focus on the striatum.
Association of genetic variants in the adiponectin gene with adiponectin level and hypertension in Hong Kong Chinese
Authors: Ong Kwok Leung , Li Mingfang , Tso Annette W K , Xu Aimin , Cherny Stacey S , Sham Pak Chung , Tse Hung Fat , Lam Tai Hing , Cheung Bernard M Y , Lam Karen S L
Published: June 2010

Objective

Low plasma adiponectin level can predict the development of hypertension after 5 years in our population. We therefore investigated whether single-nucleotide polymorphisms (SNPs) in the adiponectin gene influenced plasma adiponectin level and whether they were associated with hypertension.

Design and methods

We genotyped 14 tagging SNPs in 1616 subjects with persistent normotensive or hypertensive status during a 6.4-year follow-up period in the Hong Kong Cardiovascular Risk Factor Prevalence Study-2 (CRISPS-2). Plasma adiponectin level was measured in 1385 subjects using in-house sandwich ELISA.

Results

The minor G allele of the SNP rs266729 was significantly associated with higher odds of hypertension (odds ratio (95% confidence interval)=1.49 (1.13–1.95), P=0.0044) after adjusting for covariates. In stepwise multiple logistic regression, this SNP (P=0.006) was a significant independent factor of hypertension, together with age (P<0.001), body mass index (P<0.001), triglycerides (P=0.021), and insulin resistance index (P<0.001). Among the 14 SNPs, rs266729 (β=−0.067, P=0.0037), −10677C>T (β=0.069, P=0.0027), rs182052 (β=−0.097, P<0.0001), and rs12495941 (β=0.103, P<0.0001) were significantly associated with adiponectin level after adjusting for covariates. No significant sex interaction was found for the associations of SNPs with hypertension and adiponectin level. Similar results were obtained in haplotype analysis.

Conclusion

In our population, genetic variants in the adiponectin gene influenced plasma adiponectin levels, and one of them was associated with hypertension. This study has provided further evidence for a role of adiponectin in the development of hypertension.
From the Editors
Authors: McElhinny Bonnie , Mills Sara
Published: June 2010

Editorial
Gendered choices
Authors: Fuller Janet M.
Published: June 2010

This paper examines the use of Spanish and English, as well as collaborative discourse sequences, of four fourth graders in a bilingual classroom in terms of how they are used to construct gender identity. The analysis shows how language practices can become gendered through both societal and interactional norms and practices. The two girls’ use of English to construct their identities as best friends becomes part of the construction of femininity through the influence of both macro-social gender roles and the girls’ own linguistic repertoires and behavior in this community of practice. Further, both boys and girls use collaborative speech, but their aims of collaboration differ in ways that draw on hegemonic masculine roles in society as well as the personal agendas of the speakers.
The sociolinguistics of colonisation: a perspective of language shift
Authors: Omoniyi Tope
Published: June 2010

In this chapter I want to propose an alternative paradigm for understanding the dynamics of multilingualism, language competition and politics in the complex sociolinguistic terrain of sub-Saharan Africa. Particularly for the purpose of explaining language shift, it is important to note that African states had fought wars of expansion and taken vassal states in a ‘colonial’ era before European colonialists arrived in the region.
Worldwide decline of specialist species: toward a global functional homogenization?
Authors: Clavel Joanne , Julliard Romain , Devictor Vincent
Published: June 2010

Specialization is a concept based on a broad theoretical framework developed by evolutionary biologists and ecologists. In the past 10 years, numerous studies have reported that – in many contexts – generalist species are “replacing” specialist species. We review recent research on the concept of the ecological niche and species specialization, and conclude that (1) the observed worldwide decline in specialist species is predicted by niche theory, (2) specialist declines cause “functional homogenization” of biodiversity, and (3) such homogenization may be used to measure the impact of disturbance on communities. Homogenization at the community level could alter ecosystem functioning and productivity, as well as result in the deterioration of ecosystem goods and services. We propose community‐level specialization as an indicator of the impact of global changes (habitat and climate disturbances) on biodiversity.
Anti-alcohol Posters in Poland, 1945-1989: Diverse Meanings, Uncertain Effects
Authors: Gorsky Martin , Krajewski-Siuda Krzysztof , Dutka Wojciech , Berridge Virginia
Published: June 2010

We provide a historical study of the anti-alcohol public health poster in Poland between 1948 and 1990. Our case study illuminates public health policies under communism, with the state as the dominant force in health communication. Poland has a distinctive history of poster art, moving from a Stalinist phase of socialist realism to the diverse styles of the later Polish School. Quantitative and qualitative analysis of 213 posters establishes the major themes and differentiates community approaches, which depict the drinker as a social or political deviant, from those emphasizing individual risk. Medical issues were a minor theme, reflecting public policies geared more toward confinement than treatment. However, Polish School artists used metaphor and ambiguity, and references to the contested cultural symbolism of drink, to complicate and subvert the narrow propaganda intent. Thus, although apparently unsuccessful in restraining overall consumption, these posters offer valuable lessons for policymakers on the use of visual media in health campaigns.
Estimation of Dry-Rock Elastic Moduli Based on the Simulation of Mud-Filtrate Invasion Effects on Borehole Acoustic Logs
Authors: Odumosu Tobiloluwa B. , Torres-Verdín Carlos , Salazar Jesús M. , Ma Jun , Voss Benjamin , Wang Gong Li
Published: June 2010

Reliable estimates of dry-rock elastic properties are critical to the accurate interpretation of the seismic response of hydrocarbon reservoirs. We describe a new method for estimating elastic moduli of rocks in-situ based on the simulation of mud-filtrate invasion effects on resistivity and acoustic logs.

Simulations of mud-filtrate invasion account for the dynamic process of fluid displacement and mixing between mud-filtrate and hydrocarbons. The calculated spatial distributions of electrical resistivity are matched against resistivity logs by adjusting the underlying petrophysical properties. We then perform Biot-Gassmann fluid substitution on the 2D spatial distributions of fluid saturation with initial estimates of dry-bulk (kdry) modulus and shear rigidity (µdry) and a constraint of Poisson's ratio (?d) typical of the formation. This process generates 2D spatial distributions of compressional and shear-wave velocities and density. Subsequently, sonic waveforms are simulated to calculate shear-wave slowness. Initial estimates of the dry-bulk modulus are progressively adjusted using a modified Gregory-Pickett (1963) solution of Biot's (1956) equation to estimate a shear rigidity that converges to the well-log value of shear-wave slowness. The constraint on dynamic Poisson's ratio is then removed and a refined estimate of the dry-bulk modulus is obtained by both simulating the acoustic log (monopole) and matching the log-derived compressional-wave slowness.

This technique leads to reliable estimates of dry-bulk moduli and shear rigidity that compare well to laboratory core measurements. Resulting dry-rock elastic properties can be used to calculate seismic compressional-wave and shear-wave velocities devoid of mud-filtrate invasion effects for further seismic-driven reservoir-characterization studies.
Experimental Investigation of Emulsion Stability in Gas/Oil Separation Plants
Authors: Al-Ghamdi A. M. , Noïk C. , Dalmazzone C. , Kokal S.
Published: June 2010

This paper presents an experimental study performed to characterize the stability of emulsion samples collected from different Gas/Oil Separation Plants (GOSPs). The first part of the study (Al-Ghamdi et al. 2007) focused on the analyses of separated phases. Many techniques (differential scanning calorimetry, Karl Fischer titration, rheology, optical microscopy, and cryo-scanning electron microscopy) were applied to analyze and characterize the separated phases: crude oil, emulsion, and free water. In the second part of this study, the stability of residual emulsions was investigated against several chemical demulsifiers by using bottle tests and an automated vertical-scan macroscopic analyzer (Turbiscan; Formulaction; Toulouse, France). This instrument is used to obtain kinetics of separation of concentrated and opaque dispersed systems such as emulsions, suspensions, and foams. Interfacial tension measurements were also made to obtain information about the interfacial behavior of samples including viscoelasticity properties of the film. The results of transient emulsion-separation experiments provide some useful insights into their behavior, stability, and tightness. The study highlights the main physicochemical parameters responsible for the varying tightness of these emulsions and should help provide recommendations to optimize their treatment costs and resolve emulsion issues in the GOSPs.
Temperature Effects on Surfactant-Aided Imbibition Into Fractured Carbonates
Authors: Gupta R. , Mohanty K.
Published: June 2010

Little oil is recovered from fractured oil-wet carbonate rocks by waterflooding. Surfactant treatments are being developed to enhance oil recovery from such formations. This paper investigates the effect of temperature on such surfactant treatments. Anionic and nonionic surfactants have been identified for oil recovery from fractured low-permeability carbonate rocks at high temperatures. For most of the surfactants studied, optimal salinity decreases slightly or remains unchanged with an increase in temperature. Contact angles on initially oil-wet calcite plates decrease on addition of most of the surfactants; the final contact angle decreases with increase in temperature for all the surfactants in the current study. Oil-recovery rate from surfactant solution imbibition increases with temperature for all surfactants. At 90°C, high recovery [approximately 60% original oil in place (OOIP) in 30 days] was obtained for many surfactants at very low surfactant concentrations (< 0.1 wt%) in tight (approximately 15 md) carbonate cores. Surfactant/brine imbibition was found to be a gravity-driven process for these surfactants. Increase in temperature leads to reductions in viscosity and contact angle, which, in turn, increases oil relative permeability, which enhances the oil-recovery rate.
The Effect of Including Tracer Data in the Ensemble-Kalman-Filter Approach
Authors: Valestrand Randi , Sagen Jan , Nævdal Geir , Huseby Olaf
Published: June 2010

Tracers are widely used to increase the understanding of fluid flow; they can be used to label injection fluids, hence, well connections and fluid patterns can be established when the tracer appears in production wells. Tracer data contain valuable information but are often underexploited.

This paper presents methodology for assimilation of tracer data for reservoir model updating using the ensemble Kalman filter (EnKF). The presented assimilation methodology is generally applicable for all types of tracers, but the example used for demonstration focuses on gas tracers. Contrary to water tracers, which can be either nonpartitioning or partition between (oil and water) phases, gas tracers always partition between the oil and gas phases. This oil/gas partitioning is accounted for in the presented tracer transport modeling. The EnKF has recently gained popularity as a method for history matching. The EnKF includes online update of parameters and the dynamical states. An ensemble of model representations is used to represent the model uncertainty.

The value of tracer data in the EnKF approach is demonstrated on a North-Sea-based example. The permeability and fault transmissibility multiplier of a reservoir are estimated by EnKF. This example shows that tracer data can be used successfully in an EnKF-based automatic updating scheme. Potential misinterpretations of gas tracer data if their partitioning is neglected is highlighted by comparing results from simulation cases where partitioning is neglected to simulation results where partitioning is accounted for.
The Importance of Wax-Deposition Measurements in the Simulation and Design of Subsea Pipelines
Authors: Akbarzadeh Kamran , Ratulowski John , Eskin Dmitry , Davies Tara
Published: June 2010

Conventional practices for estimating the amount of deposited wax in pipelines are usually based on predictions made with simulation packages using limited stock-tank-oil (STO) deposition data collected under laminar-flow conditions in bench-scale flow loops. Such practices are conservative and often lead to nonoptimal designs of pipelines and surface facilities. For optimized designs, laboratory-scale deposition measurements made under realistic conditions are required to calibrate flowline models. In this work, a high-pressure deposition cell that operates on the Taylor-Couette (TC) flow principle is used to generate more deposition data with live reservoir fluids under turbulent flow similar to the conditions encountered in many flowlines. The analogy between TC flow and pipe flow is explained, and a scalability flow chart for linking the laboratory-scale deposition data from TC configuration to pipe configuration is presented. Through a case study, the scaled-deposition data are then used to tune a wax-deposition model in the OLGA®5 simulation package. Next, the tuned model is applied to predict wax deposition under actual production and transportation conditions. The importance of tuning the deposition models with live fluid data under turbulent-flow conditions is also shown by comparing results obtained from conventional dead-oil low-shear data.
A New Regression-Based Method for Accurate Measurement of Coal and Shale Gas Content
Authors: Shtepani E.. , Noll L.A.. A. , Elrod L.W.. W. , Jacobs P.M.. M.
Published: June 2010

Gas content and storage capacity are the key parameters for determination of the gas resources and reserves in unconventional reservoirs. These parameters must be obtained from laboratory experiments in core samples such as desorption canister tests and adsorption isotherm experiments. Desorption canister testing is performed to determine the total adsorbed gas content, gas composition, and the total desorption time. Adsorption isotherm experiments are conducted to determine the gas storage capacity with pressure and for CO2 sequestration purposes. Other analyses of coals include proximate analysis and bulk-density measurements of all samples. Shales are commonly analyzed for total organic carbon in lieu of proximate analysis.

The gas content is estimated by placing selected freshly cut reservoir samples in airtight sealed canisters and measuring desorbed gas volume as a function of time at atmospheric conditions. Total gas content is the summation of three components: "lost gas," desorbed gas, and "residual gas." "Lost gas" is the volume of the gas that desorbs from the sample during the recovery process at the wellsite, before the core sample can be sealed in a desorption canister. "Residual gas" is the gas that remains sorbed on the sample at the completion of the canister desorption test.

A disadvantage of this procedure is the estimation of "lost gas." The volume of the "lost gas" is usually estimated by extrapolation of desorbed data to time zero using linear and/or polynomial curve-fit to the plot of cumulative desorbed gas vs. square root of time. The differences between both methods can become more pronounced, especially in high-gas-content reservoirs.

In this paper a new method, which is based on nonlinear regression of measured gas content, is presented. This technique offers an accurate estimation of lost gas, which, coupled with sorption isotherm, has an impact on the calculation of gas in place, the recoverable reserves, and production profiles.
Predicting Hydrate-Plug Formation in a Subsea Tieback
Authors: Davies Simon R. , Boxali John A. , Koh Carolyn A. , Sloan E. Dendy , Hemmingsen Pål V. , Kinnari Keijo J. , Xu Zheng-Gang
Published: June 2010

Field data from StatoilHydro on hydrate-plug formation in the Tommeliten gas/condensate field are compared to predictions of the hydrate-growth model (CSMHyK-OLGA) for four typical operating scenarios: steady-state operation with failure of inhibitor injection, restart of an uninhibited line, restart of an underinhibited line, and restart of a depressurized line.

Although the CSMHyK model was designed for oil flowlines, the model is able to predict the correct time scale for hydrate-plug formation in this gas/condensate tieback. The predicted locations of the plugs are often farther upstream than observed in the field trials. This is mainly because of the assumption of a "hydrate/oil slip factor" of zero, which forces the hydrate to accumulate where it initially formed. In reality, hydrate agglomerates would be carried further downstream before eventually jamming in dips.

Predicting where and when hydrate plugs will form in subsea tiebacks is of increasing importance as the industry strives to manage the risk of plugging in oil and gas flowlines while minimizing the use of costly and environmentally harmful chemicals for hydrate inhibition. The Colorado School of Mines has been developing the CSMHyK model for the past 5 years, in collaboration with the SPT Group and several leading energy companies.
Experimental Study and Modeling of Cuttings Transport Using Foam With Drillpipe Rotation
Authors: Duan Mingqin , Miska Stefan , Yu Mengjiao , Takach Nicholas , Ahmed Ramadan , Hallman John
Published: June 2010

Although rotary drilling is being used in most wells, the impact of drillpipe rotation on hole cleaning during foam drilling has not been investigated. There has been no single predictive tool developed to address pipe rotation effects on foam drilling. This paper presents the first study of cuttings transport using foam with pipe rotation under simulated downhole conditions.

A field-scale, high-pressure/high-temperature wellbore simulator with a 73-ft-long, 5.76×3.5-in. eccentric annular test section was used to investigate the effects of pipe rotation, foam quality and velocity, downhole pressure and temperature on cuttings transport, and pressure losses in a horizontal wellbore. Experiments were conducted with backpressures from 100 to 400 psi and temperatures from 80 to 160°F. Pipe rotary speeds were varied from 0 to 120 RPM, with foam qualities ranging from 60 to 90% and foam velocities from 2 to 5 ft/sec.

It was found that pipe rotation not only significantly decreases cuttings concentration in a horizontal annulus but also results in a considerable reduction in frictional pressure loss. The reduction in cuttings concentration is up to 40% at a medium foam velocity (3 ft/sec) when pipe is rotated up to 120 RPM. The decrease in frictional pressure loss is up to 50% at a medium foam velocity and is more than 60% at a low velocity. Using a higher foam velocity or quality also improves hole cleaning; however, pressure losses are significantly increased.

A mechanistic model and an associated computer simulator were developed for practical design and field applications. It can be used to predict cuttings concentration, bed height, and pressure drop during horizontal foam drilling with various pipe rotary speeds, eccentricities, foam qualities, and velocities under different pressure and temperature conditions. Comparisons between model predictions and experimental results show that the difference is less than 15% in most of the cases.
Estimation of Depths of Fluid Contacts and Relative Permeability Curves by History Matching Using Iterative Ensemble-Kalman Smoothers
Authors: Wang Yudou , Li Gaoming , Reynolds Albert C.
Published: June 2010

With the ensemble Kalman filter (EnKF) or smoother (EnKS), it is easy to adjust a wide variety of model parameters by assimilation of dynamic data. We focus first on the case where realizations and estimates of the depths of the initial fluid contacts, as well as grid- block rock-property fields, are generated by matching production data with the EnKS. Then we add the parameters defining power law relative permeability curves to the set of parameters estimated by assimilating production data with EnKS. The efficiency of EnKF and EnKS arises because data are assimilated sequentially in time and so "history matching data" requires only one forward run of the reservoir simulator for each ensemble member. For EnKS and EnKF to yield reliable characterizations of the uncertainty in model parameters and future performance predictions, the updated reservoir-simulation variables (e.g., saturations and pressures) must be statistically consistent with the realizations of these variables that would be obtained by rerunning the simulator from time zero using the updated model parameters. This statistical consistency can be established only under assumptions of Gaussi- anity and linearity that do not normally hold. Here, we use iterative EnKS methods that are statistically consistent, and show that, for the problems considered here, iteration significantly improves the performance of EnKS.
Confidence Limits Associated With Values of the Earth's Magnetic Field Used for Directional Drilling
Authors: Macmillan Susan , Grindrod Steve
Published: June 2010

This paper describes updated uncertainties for use with predicted geomagnetic parameters within magnetic measurement-whiledrilling (MWD) survey-tool-error models. These models are used to define positional-error ellipsoids along the wellbore, which assist in hitting geological targets and avoiding collisions with existing wellbores.

The declination, dip angle, and total field strength of the Earth's magnetic field are used with magnetic-survey tools for surveying the wellbore. These values are often obtained from mathematical models such as the British Geological Survey (BGS) global-geomagnetic model (BGGM). As the Earth's magnetic field is continually varying with time, the BGGM is updated annually to maintain accuracy. However, a global predictive model cannot capture all sources of the Earth's magnetic field, which results in uncertainties of the predicted parameters. The Industry Steering Committee on Wellbore Surveying Accuracy (ISCWSA) published an MWD-error model in 2000 (Williamson 2000). The geomagnetic-field uncertainties that are part of this model were derived from work conducted by the BGS in the early 1990s. Since then, more-accurate data from magnetic-survey satellites have been introduced into the BGGM, and the uncertainty of the predicted geomagnetic-field parameters has been reduced.

The original approach to deriving the uncertainties involved separating the various error sources in the magnetic field and assessing them individually. This paper uses a simpler approach where clean orientated magnetic downhole data are simulated using geomagnetic-observatory data. Spot absolute measurements of the magnetic field made at observatories around the world are adjusted for the crustal magnetic field to make them more representative of hydrocarbon geology. The adjusted observatory data are then compared with the predicted values from the BGGM to assess the uncertainty. The uncertainties do not fit a normal distribution, so they are expressed as limits for various confidence levels. They vary with location and, in their derivation, do not assume any underlying empirical error distribution. While they also vary with time, we provide time-averaged look-up tables that should be valid for as long as there are good-quality satellite data on which to base global magnetic-field models. Options to reduce the uncertainties further using data from local magnetic surveys [in-field referencing (IFR)] and observatories (interpolation IFR) are also described.

The use of the revised geomagnetic uncertainty values in the MWD-error model will reduce wellbore-position uncertainty to reflect the increased accuracy from recent improvements in geomagnetic modeling. This is demonstrated using results for the ellipsoids of uncertainty output by an MWD error model for three standard ISCWSA well profiles.
Medium-Scale Experiments on Stabilizing Riser-Slug Flow
Authors: Sivertsen Heidi , Alstad Vidar , Skogestad Sigurd
Published: June 2010

This is the second of two papers describing control experiments on a medium-scale slug rig. The first paper (Sivertsen et al. 2009) describes experiments performed on a small-scale laboratory rig built at the Norwegian University of Science and Technology (NTNU) Department of Chemical Engineering. These experiments showed that, despite noisy measurements, it is possible, with feedback control, to "stabilize the flow" (i.e., to achieve reasonably smooth flow in the normally riser-induced severe slug-flow region) using only topside measurements. The question to be answered is whether these results also apply for larger riser systems.

In the present paper, we look at some results obtained from a 10-m-high, 3-in.-diameter medium-scale test rig located at the Statoil Research Centre in Porsgrunn, Norway. Several cascade control structures are tested and compared, both with each other and with the results obtained from the small-scale NTNU loop. The rig was also modeled and analyzed using a simple three-state dynamic model.

The new experiments were successful and confirm the results of Sivertsen et al. (2009) from the small-scale rig. The valve opening with nonslug flow operation could be increased from approximately 12% with no control to almost 24% with control using topside measurements only. This makes it possible to produce with a larger production rate and increase the total recovery from the producing oil field. The valve opening with control could be further increased to approximately 28% using measurements from the bottom of the riser, but such measurements may not be available in many cases.