bluuebunny/crossref_metadata_2025 huggingface dataset:
A standardized aortic aneurysm model for the assessment of endovascular stent-graft technology
Authors: Macierewicz J A , Albertini J-N , Hinchliffe R J
Published: April 2011

Reliable models of aortic aneurysms are required to test endovascular stent-graft technology prior to human use. We describe the creation of a standardized prosthetic aneurysm in an ovine model to assess endovascular technology. In an adult ovine model under general anesthesia, a polyester sphere measuring 6 cm across was sutured onto the infrarenal aorta following aortotomy. Two weeks later an endovascular stent-graft was deployed in the aorta. Exclusion was confirmed on monthly ultrasound duplex and during angiography at three months and under terminal anesthesia at six months. Autopsy along with histology of the specimen were then performed. A total of 10 sheep underwent aneurysm implantation. Nine received a straight tube endovascular stent-graft (Lombard Medical, Abingdon, Oxon, UK) and seven completed the study. Five prosthetic aneurysms shrank during serial imaging with duplex ultrasound and angiography. However, two remained the same size. One of these had a type I endoleak whereas the other had endotension (type I endoleak confirmed at autopsy). This animal model provides a reliable and reproducible method of creating prosthetic aneurysms for assessing endovascular stent-grafts. It was possible to assess aneurysm exclusion non-invasively using duplex ultrasound. Aneurysms effectively excluded from the circulation shrank whereas those with an endoleak did not.
Evolution of Coal Structures: FTIR Analyses of Experimental Simulations and Naturally Matured Coals in the Ordos Basin, China
Authors: Yao Suping , Zhang Ke , Jiao Kun , Hu Wenxuan
Published: April 2011

A series of coals of varying rank, from brown coal to anthracite, were studied by Fourier transform infrared spectroscopy (FTIR). Curve-fitting analysis was employed to characterize coal structural evolution during the coalification process. The study was carried out on samples of a natural evolutionary series as well as experimental simulation coals dispersed on KBr pellets throughout the Ordos Basin, China. The results showed that the infrared spectrum of coal allowed quality and even quantity identification of the degree of coalification. Oxygen-containing groups and alkyl side chains of coal cracked at different rates with increasing degree of coalification. The cracking rates were divided into three stages according to the main changes in coal structure. These stages were carboxyl groups, fat groups and aromatic rings. Carboxyl groups decreased when Ro was less than 0.5%, and these groups were maintained until the fat coal stage began. Fat groups mainly cracked at the asphaltization stage and formed abundant hydrocarbons. These groups were the main sources for the formation of immature and low maturity, coal-generating oil before asphaltization. In the high evolutionary stage, after asphaltization, all alkyl side chains in the coal had cracked, while the degree of condensed aromatic rings had increased greatly. The ratios of aromatic hydrocarbons (3000 to 3100 cm−1) to aliphatic carbons (2800 to 3000 cm−1), CH2/CH3 (2920/2950 cm−1) and carboxyl groups to aromatic carbons (1705/1620 cm−1 + 1600cm−1 + 1580 cm−1) appeared to be suitable parameters for assessing the natural maturation of coal.
Characteristics of High Rank Coalbed Methane Reservoir from the Xiangning Mining Area, Eastern Ordos Basin, China
Authors: Ding Shuli , Zhu Jiangang , Zhen Baiping , Liu Zhanyong , Liu Qinfu
Published: April 2011

For the purpose of better estimating the CBM resource potential in the study area, the high rank CBM reservoirs were studied by geological surveys and laboratory measurements in Xiangning mining area, eastern Ordos Basin. Geological characteristics of coals in the Xiangning mining area provide favourable conditions for the development of CBM reservoirs. Coal seams are dominated by semibright coal, which are all low volatile anthracite coal with Rmax ranging from 2.22 to 2.50%. No. 2, 3 and 10 coal seams are vitrinite–rich (81.2%, averagely) and low to middle ash yield coals (16.86–21.49%, averagely). The permeability values of coal reservoirs range form 0.0067 to 0.268 mD, and the porosity is from 2.82 to 4.14% in the study area. Microfractures are mainly tensile structure, pores of coals are dominated by macropores, mesopores came next to it followed by micropores, and the great majority of induced porosity is stomas in the study area. No. 2, 3 and 10 CBM reservoirs are characterized by higher gas capacities (26.08 to 27.27 m3/t, VL). The gas content of CBM reservoirs has a positive correlation with the burial depth.
Sedimentary Systems and Their Influences on Gas Distribution in the Second Member and Third Member of the Permian Xiashihezi Formation in the Daniudi Gas Field, Ordos Basin, China
Authors: Jiang Zaixing , Xu Jie , Chen Zhaoyou , Lin Wen
Published: April 2011

Based on the study of cores, analytical data and statistics data from the second member and the third member of the Permian Xiashihezi Formation (P1x2 and P1x3) in the Daniudi Gas Field, Ordos basin, China, the shore-shallow lake deposition can be confirmed in the study area for the first time. The discovery of tempestite deposition and the sandbody reworked by lacustrine waves can be inferred by the observation of cores. The presence of type II1 kerogen indicates stable infralittoral deposits in this area. Also, the analysis of chemical elements indicates that the water depth became deeper from north to south and that the deposition environment changed from onshore to underwater. Moreover, the distribution of mudstone colors reveals that the lake shoreline changed over different periods. Based on the study of sedimentary facies and the statistics of the gas pool, the closed relationship between lake shoreline and the distribution of the gas pools is conformed.
Modeling the Gas-Solid Flow in Calcining Furnace
Authors: Luo Haiyan
Published: April 2011

Gas-solid two-phase flow in calcining furnace is investigated in this paper. The turbulent fluid phase is calculated using the RNG k- e two-equation model in the Eulerain framework while the solid phase being handled via the particle stochastic trajectory model is calculated in the Lagrangian framework. Flow pattern characteristics of the fluid phase and the particle trajectories of the solid phase were predicted subject to a range of flow conditions and different particle sizes. The computed results provided useful information in the preview of kinetics regulation of the gas-solid two-phase in calcining furnace.
Grid Generation Issues in the CFD Modelling of Two-Phase Flow in a Pipe
Authors: Hernandez-Perez V. , Abdulkadir M. , Azzopardi B.J.
Published: April 2011

The grid generation issues found in the 3D simulation of two-phase flow in a pipe using Computational Fluid Dynamics (CFD) are discussed in this paper. Special attention is given to the effect of the element type and structure of the mesh. The simulations were carried out using the commercial software package STAR-CCM+, which is designed for numerical simulation of continuum mechanics problems. The model consisted of a cylindrical vertical pipe. Different mesh structures were employed in the computational domain. The condition of two-phase flow was simulated with the Volume of Fluid (VOF) model, taking into consideration turbulence effects using the k-e model. The results showed that there is a strong dependency of the flow behaviour on the mesh employed. The best result was obtained with the grid known as butterfly grid, while the cylindrical mesh produced misleading results. The simulation was validated against experimental results.
The Impact of Three Different Cumulus Parameterization Schemes on the Indian Summer Monsoon Circulation
Authors: Singh AP , Singh R. P. , Raju P.V. S. , Bhatla R.
Published: April 2011

In the present paper, the regional model (MM5) has been used to evaluate the performance of three cumulus parameterization schemes (CPSs, namely, the Anthes-Kuo, Bette-Miller and Grell) over the Indian summer monsoon season of 1998. The model was integrated at 90 km horizontal resolution for the peak monsoon period of July, 1998. The initial and boundary conditions were taken from the National Center for Environmental Prediction (NCEP) reanalysis available at 2.5° horizontal resolution. The performance of these CPSs has been examined using precipitation, wind, surface air temperature and heat – moisture data. Features of the Indian summer monsoon are found to be fairly well simulated by these three schemes; however, some differences are found in the typical features of the Indian summer monsoon. The strength of low level westerly jet, the cross equatorial flow, and the tropical easterly Jet have emerged clearly in the simulation using Grell compared to other CPSs. The Grell cumulus convection scheme shows ascending motion over whole tropical monsoon region and descending motion in mid latitude and is found to show close resemblance with the reanalysis data. The model simulation with Kuo cumulus scheme shows descending motion over tropical region, which is found to be unrealistic during monsoon and provide under estimation of rainfall over the Indian region. Strong upward motion over oceanic region by the model using Betts-Miller and Kuo schemes is also found to be unrealistic. The simulation of heat and moisture budget, and distribution of rainfall during monsoon period over Indian subcontinent are found to be improved considerably using Grell scheme as compared to other CPSs, whereas using Kuo scheme, rainfall is found to be underestimated over Indian subcontinent.
The ISO/EN 13606 Standard for the Interoperable Exchange of Electronic Health Records
Authors: Muñoz Pilar , Trigo Jesús D. , Martínez Ignacio , Muñoz Adolfo , Escayola Javier , García José
Published: April 2011

The standardization of Electronic Health Records (EHR) is a crucial factor for ensuring interoperable sharing of health data. During recent decades, a plethora of initiatives ‐ driven by international organizations ‐ has emerged to define the required models describing the exchange of information between EHRs. These models cover different essential characteristics for building interoperable EHRs, such as architecture, methodology, communication, safety or terminology, among others. In this context, the European reference frame for the standardized exchange of EHR is the recently approved ISO/EN 13606 standard. This multi‐part standard provides the syntactic and semantic capabilities (through a dual model approach) as well as terminology, security and interface considerations for the standardized exchange of EHR. This paper provides (a) an introduction to the different standardization efforts related to the interoperable exchange of EHR around the world, and (b) a description of how the ISO/EN 13606 standard provides interoperable sharing of clinical information.
A Clinical Database‐Driven Approach to Decision Support: Predicting Mortality Among Patients with Acute Kidney Injury
Authors: Celi Leo Anthony G. , Tang Robin J. , Villarroel Mauricio C. , Davidzon Guido A. , Lester William T. , Chueh Henry C.
Published: April 2011

In exploring an approach to decision support based on information extracted from a clinical database, we developed mortality prediction models of intensive care unit (ICU) patients who had acute kidney injury (AKI) and compared them against the Simplified Acute Physiology Score (SAPS). We used MIMIC, a public de‐identified database of ICU patients admitted to Beth Israel Deaconess Medical Center, and identified 1400 patients with an ICD9 diagnosis of AKI and who had an ICU stay ≥3 days. Multivariate regression models were built using the SAPS variables from the first 72 hours of ICU admission. All the models developed on the training set performed better than SAPS (AUC = 0.64, Hosmer‐Lemeshow p <0.001) on an unseen test set; the best model had an AUC = 0.74 and Hosmer‐Lemeshow p = 0.53. These findings suggest that local customized modeling might provide more accurate predictions. This could be the first step towards an envisioned individualized point‐of‐care probabilistic modeling using one′s clinical database.
Dynamic Response of Stiffened Plates under Air Blast
Authors: Goel Manmohan Dass , Matsagar Vasant A. , Gupta Anil K.
Published: April 2011

A numerical investigation is presented to examine the effect of stiffener configuration on the response of rectangular plate subjected to air blast loading. Dynamic response of the plate, with various stiffener layouts under air blast is analysed. The plate is modelled using shell elements and the effect of strain rates are considered using Johnson-Cook (J-C) model, under air blast load applied in the form of an equivalent rectangular uniform pulse. A modal analysis is carried out to obtain the natural frequencies of the plates that help in assessment and influence on their dynamic response. Analysis is carried out from the perspective of understanding the dynamic response of the plate, with stiffener, in comparison with equivalently thickened unstiffened plate. The results indicate that the equivalently thickened unstiffened plates exhibit higher peak displacement as compared to the stiffened plate, signifying the importance of the stiffeners placed strategically. It is concluded that the stiffener layout and strain rate consideration governs the dynamic response of the plates subjected to small duration blast loading.
Blast Pressure Distribution on a Buried Obstacle in a Porous Wet Soil
Authors: Feldgun V.R. , Karinski Y.S. , Yankelevsky D.Z.
Published: April 2011

The paper presents a comprehensive approach to simulate the blast pressure distribution on a rigid or flexible planar or curved obstacle buried in a porous soil medium. The Lyakhov three-phase model is adopted to take into account the volumetric components of the soil medium (air, water, and solid matrix) and their properties, in the formulation of all the branches of the equation of state that simulates the soil. The present approach considers both the bulk and the shear elastic-plastic behavior, including the effect of soil pressure on the yield strength for the stress tensor deviator. Both Godunov and the variational-difference methods are applied to solve the problem of blast wave propagation within the soil medium. An example problem of an explosion in a porous medium is presented, and the analysis of the soil-obstacle interaction under the blast action using the proposed method shows good correspondence with available experimental results. The pressure distribution along the envelope of a rigid obstacle has been investigated for different standoff distances of the explosive from the obstacle as well as for different levels of soil water contents up to saturation. In addition, the plane problems of blast response of a thin-walled lining that is buried in this medium has been studied for different levels of water content and the lining's extreme deformation including its dynamic buckling under the blast high pressures was investigated.
Resistance of Concrete Masonry Walls with Membrane Catcher Systems Subjected to Blast Loading
Authors: Moradi Lee G. , Dinan Robert J. , Bewick Bryan T. , Davidson James S.
Published: April 2011

This paper describes a methodology for analyzing the impulse pressure response of unreinforced concrete masonry walls that have been retrofitted with membranes that are not bonded to the masonry (catcher systems). Membrane catcher systems can be used to protect building occupants from secondary debris resulting from blast pressure, and the effectiveness of systems comprised of polymers, composites, geotextiles, and thin steel and aluminum sheets has been researched extensively over the past fifteen years. The methodology presented herein is based upon the large displacement response of the unreinforced masonry wall, with and without compression membrane arching, and the subsequent tension membrane resistance of the catcher system. The necessary equations are developed in the form of nonlinear resistance functions, which are then used in single-degree-of-freedom analyses to develop dynamic response predictions. The applicability of the approach is substantiated through comparison to full-scale blast test results, and demonstrations involving disparate materials and loading are made.
Global Formulary Review: How Do We Integrate Pharmacogenomic Information?
Authors: Poppe Lindsey B , Roederer Mary W
Published: April 2011

Objective:

To summarize a standard formulary decision process and provide recommendations for the integration of pharmacogenomic (PGx) information within the formulary decision-making process.

Data Sources:

With use of MEDLINE (1920-March 2010). the terms “formularies, hospital” and “pharmacogenetics” were searched in the MeSH database, yielding no results. The MeSH terms were then searched separately in addition to searching for “rational drug therapy” and “essential medicines list” through the main PubMed database.

Study Selection and Data Extraction:

Articles deemed relevant to both terms were assessed, interpreted, and incorporated as key pieces to the review of formularies and the integration of PGx information as a part of the formulary review process. The articles referenced were deemed appropriate and categorized into 5 areas: formulary management systems and pharmacy and therapeutics (P&T) committees, international formularies, formulary decision-making. PGx evidence, and recommendations regarding integrating PGx into formulary decision-making.

Data Synthesis:

The field of PGx is rapidly evolving as the evidence supporting genetically guided individualized therapy continues to grow. To bring this evidence from the bench to the bedside, institutions will need to evaluate PGx data to integrate individualized therapy into practice. Few standardized methods exist to analyze and apply clinical PGx data and incorporate the information into drug evaluation at the formulary level. Several online sites provide resources to aid in formulary review and can be used when incorporating clinically relevant PGx information into a formulary decision. In addition, there are key questions that organizations can ask as they evaluate the PGx information in each step of the decision-making process.

Conclusions:

P&T committees should formulate a plan to integrate a search for pharmacogenomic data with each drug evaluation and integrate the results into the formulary decision process to enhance the appraisal of drug efficacy, safety, and cost.
An In-Depth Analysis of Medication Errors in Hospitalized Patients with HIV
Authors: Snyder Ann M , Klinker Kenneth , Orrick Joanne J , Janelle Jennifer , Winterstein Almut G
Published: April 2011

Background

It is well recognized that medication errors occur and can affect success in treating patients with HIV/AIDS. However, little information is available describing the prevalence, nature, and causes of medication errors.

Objective:

To determine the incidence of combination antiretroviral therapy (ART)– and opportunistic infection (OI)–related medication errors and describe the nature and cause(s) of errors to guide future interventions.

Methods:

A daily antiretroviral utilization report was used to identify adults who were receiving ART and had been admitted to a tertiary care teaching hospital during 2 consecutive months in 2005. Patients’ charts, medication profiles, and medication administration records were reviewed for medication errors such as improper dosing, interactions, drug omissions, and missing doses. Once identified, etiology and cause were further investigated through provider interviews. An interdisciplinary team reviewed each case to establish validity of the error, severity, and cause.

Results:

Sixty-nine combined ART- and OI-related medication errors were identified in 20 of 26 (77%) evaluated patients, with 2.7 medication errors per patient. Fifty-four percent of the errors occurred within the first 24 hours after admission. Inadequate medication reconciliation on admission caused 21 of 37 (57%) admission-related errors. The most prevalent error types included missing doses (20%), underdosing (13%), overdosing (13%), therapy omission (13%). and drug-drug interaction (12%). The primary cause of errors was provider lack of knowledge.

Conclusions:

Prospective investigation of medication errors provided in-depth insight into the diverse nature of HIV-related medication errors, risk factors, and potential preventive strategies. System changes such as hard stops in the clinical decision support software and improved medication reconciliation training, and changes in cart-fill time could prevent specific types of errors. Further studies are warranted to evaluate the impact of various strategies for preventing medication errors in the HIV population.
Experienced action constructions in Umpithamu: Involuntary experience, from bodily processes to externally instigated actions
Authors: Verstraete Jean-Christophe
Published: April 2011

This paper is a semantic analysis of ‘experienced action’ constructions in Umpithamu, a Paman language from Cape York Peninsula (Australia). The basic argument is that these constructions are related to the better-attested category of experiencer object constructions (e.g. Evans, Non-nominative subjects 1: 69–192, 2004), which in Umpithamu describe involuntary experience of bodily processes. Experienced action constructions extend the feature of ‘involuntary experience’ from processes within the body to actions originating outside the body, and thus provide a semantically marked alternative for standard transitive clauses. The constructions are typologically interesting because they show the need to identify different loci of experiential semantics in a construction, and they help to clarify the status of control for human Undergoers within semantic typologies of reduced transitivity.
German children's productivity with simple transitive and complement-clause constructions: Testing the effects of frequency and variability
Authors: Brandt Silke , Verhagen Arie , Lieven Elena , Tomasello Michael
Published: April 2011

The development of abstract schemas and productive rules in language is affected by both token and type frequencies. High token frequencies and surface similarities help to discover formal and functional commonalities between utterances and categorize them as instances of the same schema. High type frequencies and diversity help to develop slots in these schemas, which allow the production and comprehension of novel utterances. In the current study we looked at both token and type frequencies in two related constructions in German child-directed speech: simple transitive and complement-clause constructions. Both constructions contain high frequency verbs, which potentially support the development of verb-specific schemas. However, only the frequent verbs in the transitive constructions occur with a variety of subject types, which also supports the development of a slot in the subject position.

We then used an elicited production task to compare 4- and 5-year-old German-speaking children's productivity with simple transitive constructions and complement-clause constructions. The children were prompted to change the subjects of high and low frequency simple transitive verbs, such as essen ‘eat’ and naschen ‘nibble’, mental-state complement-taking verbs, such as denken ‘think’ and vermuten ‘presume’, and communication complement-taking verbs, such as sagen ‘say’ and berichten ‘report’. In accordance with earlier findings, children had less difficulty producing new utterances with high frequency transitive verbs than with low frequency transitive verbs. For the other verb classes, however, we found either reverse frequency effects or no frequency effects. For these verb classes, children's productivity can be determined by diversity rather than simple token frequency. We discuss how token frequency interacts with diversity, discourse function, semantic complexity, and syntactic complexity.
Novel Scheme of Multi-Rate Quasi-synchronous Coherent Time-spreading OCDMA System
Authors: Ji Jianhua , Xiao Zhengfeng
Published: April 2011

We propose a novel scheme of multi-rate quasi-synchronous coherent time-spreading OCDMA system, employing orthogonal variable spreading factor (OVSF) codes with a zero-correlation zone. Within permissible time delay, the aperiodic cross-correlation of OVSF with a zero-correlation zone equals zero. Therefore, multiple-access interference and beat noise can be removed in multirate quasi-synchronous coherent time-spreading OCDMA system, and the near-far problem can also be eliminated. Simulation of eight simultaneous users with 2.5 Gbit/s, 1.25 Gbit/s and 0.625 Gbit/s is demonstrated, where the fiber link consists of 20 km single-mode fiber, plus 2 km Dispersion Compensating Fiber. The results show that OVSF codes with a zero-correlation zone can be employed to multi-rate quasi-synchronous coherent time-spreading OCDMA system.
Performance Comparison of BB84 and B92 Satellite-Based Free Space Quantum Optical Communication Systems in the Presence of Channel Effects
Authors: Etengu R. , Abbou F. M. , Wong H. Y. , Abid A. , Nortiza N. , Setharaman A.
Published: April 2011

The performance of single photon pulsed polarization based BB84 and B92 platforms against individual attacks for free space quantum optical communication links between a ground station and a satellite in the low earth orbit is compared. The comparison is attained by evaluating the quantum bit error rate and secure communication bit rate on secure optical link loss and the sensitivity of different parameters. Precisely, realistic experimental parameters are used and the obtained results are compared with those of other papers. Quantum bit error rates as low as 3.5% have been regularly obtained. Moreover, with repetition rate of 10MHz at the low earth orbit standard orbital altitude of 100 km and at zenith angle of 60 degrees, secure communication bit rates of ~ 280 kHz and ~ 70 kHz were received for the BB84 and B92, respectively. The obtained results show that the BB84 protocol exhibits better performance than B92 in the distribution of the secure communication key over long distance. Overall, these results reveal that it is possible to obtain secure key exchange in the low earth orbit, an idea which can be extended to other long distance laser links such as geostationary orbit.
AKAP Signaling in Reinstated Cocaine Seeking Revealed by iTRAQ Proteomic Analysis
Authors: Reissner Kathryn J. , Uys Joachim D. , Schwacke John H. , Comte-Walters Susanna , Rutherford-Bethard Jennifer L. , Dunn Thomas E. , Blumer Joe B. , Schey Kevin L. , Kalivas Peter W.
Published: April 2011

To identify candidate proteins in the nucleus accumbens (NAc) as potential pharmacotherapeutic targets for treating cocaine addition, an 8-plex iTRAQ (isobaric tag for relative and absolute quantitation) proteomic screen was performed using NAc tissue obtained from rats trained to self-administer cocaine followed by extinction training. Compared with yoked-saline controls, 42 proteins in a postsynaptic density (PSD)-enriched subfraction of the NAc from cocaine-trained animals were identified as significantly changed. Among proteins of interest whose levels were identified as increased was AKAP79/150, the rat ortholog of human AKAP5, a PSD scaffolding protein that localizes signaling molecules to the synapse. Functional downregulation of AKAP79/150 by microinjecting a cell-permeable synthetic AKAP (A-kinase anchor protein) peptide into the NAc to disrupt AKAP-dependent signaling revealed that inhibition of AKAP signaling impaired the reinstatement of cocaine seeking. Reinstatement of cocaine seeking is thought to require upregulated surface expression of AMPA glutamate receptors, and the inhibitory AKAP peptide reduced the PSD content of protein kinase A (PKA) as well as surface expression of GluR1 in NAc. However, reduced surface expression was not associated with changes in PKA phosphorylation of GluR1. This series of experiments demonstrates that proteomic analysis provides a useful tool for identifying proteins that can regulate cocaine relapse and that AKAP proteins may contribute to relapse vulnerability by promoting increased surface expression of AMPA receptors in the NAc.
Changes in “Top-Down” Connectivity Underlie Repetition Suppression in the Ventral Visual Pathway
Authors: Ewbank Michael P. , Lawson Rebecca P. , Henson Richard N. , Rowe James B. , Passamonti Luca , Calder Andrew J.
Published: April 2011

Repetition of the same stimulus leads to a reduction in neural activity known as repetition suppression (RS). In functional magnetic resonance imaging (fMRI), RS is found for multiple object categories. One proposal is that RS reflects locally based “within-region” changes, such as neural fatigue. Thus, if a given region shows RS across changes in stimulus size or view, then it is inferred to hold size- or view-invariant representations. An alternative hypothesis characterizes RS as a consequence of “top-down” between-region modulation. Differentiating between these accounts is central to the correct interpretation of fMRI RS data. It is also unknown whether the same mechanisms underlie RS to identical stimuli and RS across changes in stimulus size or view. Using fMRI, we investigated RS within a body-sensitive network in human visual cortex comprising the extrastriate body area (EBA) and the fusiform body area (FBA). Both regions showed RS to identical images of the same body that was unaffected by changes in body size or view. Dynamic causal modeling demonstrated that changes in backward, top-down (FBA-to-EBA) effective connectivity play a critical role in RS. Furthermore, only repetition of the identical image showed additional changes in forward connectivity (EBA-to-FBA). These results suggest that RS is driven by changes in top-down modulation, whereas the contribution of “feedforward” changes in connectivity is dependent on the precise nature of the repetition. Our results challenge previous interpretations regarding the underlying nature of neural representations made using fMRI RS paradigms.
Loss of System xc−Does Not Induce Oxidative Stress But Decreases Extracellular Glutamate in Hippocampus and Influences Spatial Working Memory and Limbic Seizure Susceptibility
Authors: De Bundel Dimitri , Schallier Anneleen , Loyens Ellen , Fernando Ruani , Miyashita Hirohisa , Van Liefferinge Joeri , Vermoesen Katia , Bannai Shiro , Sato Hideyo , Michotte Yvette , Smolders Ilse , Massie Ann
Published: April 2011

System xc−exchanges intracellular glutamate for extracellular cystine, giving it a potential role in intracellular glutathione synthesis and nonvesicular glutamate release. We report that mice lacking the specific xCT subunit of system xc−(xCT−/−) do not have a lower hippocampal glutathione content, increased oxidative stress or brain atrophy, nor exacerbated spatial reference memory deficits with aging. Together these results indicate that loss of system xc−does not induce oxidative stressin vivo. YoungxCT−/−mice did however display a spatial working memory deficit. Interestingly, we observed significantly lower extracellular hippocampal glutamate concentrations inxCT−/−mice compared to wild-type littermates. Moreover, intrahippocampal perfusion with system xc−inhibitors lowered extracellular glutamate, whereas the system xc−activatorN-acetylcysteine elevated extracellular glutamate in the rat hippocampus. This indicates that system xc−may be an interesting target for pathologies associated with excessive extracellular glutamate release in the hippocampus. Correspondingly, xCT deletion in mice elevated the threshold for limbic seizures and abolished the proconvulsive effects ofN-acetylcysteine. These novel findings sustain that system xc−is an important source of extracellular glutamate in the hippocampus. System xc−is required for optimal spatial working memory, but its inactivation is clearly beneficial to decrease susceptibility for limbic epileptic seizures.
The Down Syndrome Critical Region Regulates Retinogeniculate Refinement
Authors: Blank Martina , Fuerst Peter G. , Stevens Beth , Nouri Navid , Kirkby Lowry , Warrier Deepti , Barres Ben A. , Feller Marla B. , Huberman Andrew D. , Burgess Robert W. , Garner Craig C.
Published: April 2011

Down syndrome (DS) is a developmental disorder caused by a third chromosome 21 in humans (Trisomy 21), leading to neurological deficits and cognitive impairment. Studies in mouse models of DS suggest that cognitive deficits in the adult are associated with deficits in synaptic learning and memory mechanisms, but it is unclear whether alterations in the early wiring and refinement of neuronal circuits contribute to these deficits. Here, we show that early developmental refinement of visual circuits is perturbed in mouse models of Down syndrome. Specifically, we find excessive eye-specific segregation of retinal axons in the dorsal lateral geniculate nucleus. Indeed, the degree of refinement scales with defects in the “Down syndrome critical region” (DSCR) in a dose-dependent manner. We further identifyDscam(Down syndrome cell adhesion molecule), a gene within the DSCR, as a regulator of eye-specific segregation of retinogeniculate projections. AlthoughDscamis not the sole gene in the DSCR contributing to enhanced refinement in trisomy,Dscamdosage clearly regulates cell spacing and dendritic fasciculation in a specific class of retinal ganglion cells. Thus, altered developmental refinement of visual circuits that occurs before sensory experience is likely to contribute to visual impairment in individuals with Down syndrome.
Deep Brain Stimulation of the Subthalamic Nucleus Alters the Cortical Profile of Response Inhibition in the Beta Frequency Band: A Scalp EEG Study in Parkinson's Disease
Authors: Swann Nicole , Poizner Howard , Houser Melissa , Gould Sherrie , Greenhouse Ian , Cai Weidong , Strunk Jon , George Jobi , Aron Adam R.
Published: April 2011

Stopping an initiated response could be implemented by a fronto-basal-ganglia circuit, including the right inferior frontal cortex (rIFC) and the subthalamic nucleus (STN). Intracranial recording studies in humans reveal an increase in beta-band power (∼16–20 Hz) within the rIFC and STN when a response is stopped. This suggests that the beta-band could be important for communication in this network. If this is the case, then altering one region should affect the electrophysiological response at the other. We addressed this hypothesis by recording scalp EEG during a stop task while modulating STN activity with deep brain stimulation. We studied 15 human patients with Parkinson's disease and 15 matched healthy control subjects. Behaviorally, patients OFF stimulation were slower than controls to stop their response. Moreover, stopping speed was improved for ON compared to OFF stimulation. For scalp EEG, there was greater beta power, around the time of stopping, for patients ON compared to OFF stimulation. This effect was stronger over the right compared to left frontal cortex, consistent with the putative right lateralization of the stopping network. Thus, deep brain stimulation of the STN improved behavioral stopping performance and increased the beta-band response over the right frontal cortex. These results complement other evidence for a structurally connected functional circuit between right frontal cortex and the basal ganglia. The results also suggest that deep brain stimulation of the STN may improve task performance by increasing the fidelity of information transfer within a fronto-basal-ganglia circuit.
Fragile X Mental Retardation Protein Regulates Protein Expression and mRNA Translation of the Potassium Channel Kv4.2
Authors: Gross Christina , Yao Xiaodi , Pong Dan L. , Jeromin Andreas , Bassell Gary J.
Published: April 2011

A prominent characteristic of the inherited intellectual impairment disease fragile X syndrome (FXS) is neuronal hyperexcitability, resulting in a variety of symptoms, such as hyperactivity, increased sensitivity to sensory stimuli, and a high incidence of epileptic seizures. These symptoms account for a significant part of the disease pattern, but the underlying molecular mechanisms of neuronal hyperexcitability in FXS remain poorly understood. FXS is caused by loss of expression of fragile X mental retardation protein (FMRP), which regulates synaptic protein synthesis and is a key player to limit signaling pathways downstream of metabotropic glutamate receptors 1/5 (mGlu1/5). Recent findings suggest that FMRP might also directly regulate voltage-gated potassium channels. Here, we show that total and plasma membrane protein levels of Kv4.2, the major potassium channel regulating hippocampal neuronal excitability, are reduced in the brain of an FXS mouse model. Antagonizing mGlu5 activity with 2-methyl-6-(phenylethynyl)-pyridine (MPEP) partially rescues reduced surface Kv4.2 levels inFmr1knock-out (KO) mice, suggesting that excess mGlu1/5 signal activity contributes to Kv4.2 dysregulation. As an additional mechanism, we show that FMRP is a positive regulator of Kv4.2 mRNA translation and protein expression and associates with Kv4.2 mRNAin vivoandin vitro. Our results suggest that absence of FMRP-mediated positive control of Kv4.2 mRNA translation, protein expression, and plasma membrane levels might contribute to excess neuronal excitability inFmr1KO mice, and thus imply a potential mechanism underlying FXS-associated epilepsy.
Shell-Isolated Nanoparticle-Enhanced Raman Spectroscopy (SHINERS) Based on Gold-Core Silica-Shell Nanorods
Authors: Li Song-Bo , Li Li-Mei , Anema Jason R. , Ren Bin , Sun Jian-Jun , Tian Zhong-Qun
Published: April 2011

Fairly monodisperse “dog bone” shaped gold nanorods were obtained clean and in high yield. Their average aspect ratio could be adjusted from ∼ 2 to ∼ 3 by altering the amount of silver nitrate present in the growth solution. They were coated with a uniform, ultrathin shell of silica and used to detect parathion pesticide on an orange peel by shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS).
Comprehensive cross production system assessment of the impact of in vitro microenvironment on the expression of messengers and long non-coding RNAs in the bovine blastocyst
Authors: Côté Isabelle , Vigneault Christian , Laflamme Isabelle , Laquerre Joanie , Fournier Éric , Gilbert Isabelle , Scantland Sara , Gagné Dominic , Blondin Patrick , Robert Claude
Published: April 2011

In vitroproduction (IVP) of cattle embryos over the past two decades has revealed several negative impacts that have been attributed to the artificial microenvironment. Studies on embryos producedin vitroclearly point to aberrant gene expression levels. So far, the causal association between phenotype and measured gene expression has not led to substantial improvement of IVP systems. The aim of this study was to generate a unique dataset composed of microarray-derived relative transcript abundance values for blastocysts produced in tenin vitrosystems differing primarily in culture medium formulation. Between-group comparisons determine the level of overall similarity among systems relative toin vivoreference embryos. The use of the dataset to contrast allin vitrotreatments with thein vivoblastocysts pointed to a single common gene network. The ‘boutique’ array contained a panel of novel uncharacterized transcripts that were variably expressed depending on the medium in which the blastocysts were produced. These novel transcripts were differentially expressed in blastocysts even as carryover from conditions encountered 7 days earlier during oocyte maturation. All of the selected novel candidates thus expressed were from intergenic regions. The function of this long non-coding RNA remains unknown but clearly points to an additional level of complexity in early embryo development.
Oral Health Behaviors, Periodontal Disease, and Pathogens in Preeclampsia: A Case‐Control Study in Korea
Authors: Ha Jung‐Eun , Oh Kyung‐Joon , Yang Hye‐Jin , Jun Jong‐Kwan , Jin Bo‐Hyoung , Paik Dai‐Il , Bae Kwang‐Hak
Published: April 2011

Background: The aim of this study is to confirm the association among oral health behaviors, periodontitis, and preeclampsia in Korean women.

Methods: This study is designed as a case‐control study. Sixteen women with preeclampsia and 48 without preeclampsia post‐delivery were included in this study from November 2007 to January 2010. Information was collected on demographics, health behaviors, and obstetric and systemic diseases that may influence the periodontal condition and preeclampsia. Full‐mouth periodontal probing was conducted by one trained examiner (KHB). Localized periodontitis was defined as periodontal clinical attachment loss (AL) ≥3.5 mm on two or three sites not on the same tooth. In addition, generalized periodontitis was defined as clinical AL ≥3.5 mm on ≥4 sites not on the same tooth. Gingival crevicular fluid was collected using a sterilized paper point for quantitative analysis of Treponema denticola, Porphyromonas gingivalis, Prevotella intermedia (Pi), and Tannerella forsythia (previously T. forsythensis).

Results: After adjusting for confounders, the adjusted odds ratio (OR) was 4.79 (95% confidence interval [CI]: 1.02 to 29.72) for localized periodontitis and 6.60 (95% CI: 1.25 to 41.61) for generalized periodontitis. In addition, the proportion of floss or interdental brush users in women with preeclampsia was lower than that in women without (adjusted OR: 0.21; 95% CI: 0.02 to 0.93). Pi was significantly more prevalent in women with preeclampsia (P = 0.028).

Conclusion: These results indicate that preeclampsia could be associated with the maternal periodontal condition and interdental cleaning.
Effects of Surfactant-Emulsified Oil-Based Mud on Borehole Resistivity Measurements
Authors: Salazar Jesús M. , Torres-Verdín Carlos , Li Wang Gong
Published: April 2011

We quantify the influence of oil-based mud (OBM)-filtrate invasion and formation-fluid properties on the spatial distribution of fluid saturation and electrical resistivity in the near-wellbore region. The objective is to appraise the sensitivity of borehole resistivity measurements to the spatial distribution of fluid saturation resulting from the compositional mixing of OBM and in-situ hydrocarbons.

First, we consider a simple two-component formulation for the oil phase (OBM and reservoir oil) wherein the components are first-contact miscible. A second approach consists of adding water and surfactant to a multicomponent OBM invading a formation saturated with multiple hydrocarbon components. Simulations also include presence of irreducible, capillary-bound, and movable water. The dynamic process of OBM invasion causes component concentrations to vary with space and time. In addition, the relative mobility of the oil phase varies during the process of invasion because oil viscosity and oil density are both dependent on component concentrations.

Presence of surfactants in the OBM is simulated with a commercial adaptive implicit compositional formulation that models the flow of three-phase multicomponent fluids in porous media. Simulations of the process of OBM invasion yield 2D spatial distributions of water and oil saturation that are transformed into spatial distributions of electrical resistivity. Subsequently, we simulate the corresponding array-induction measurements assuming axial-symmetric variations of electrical resistivity.

We perform sensitivity analyses on field measurements acquired in a well that penetrates a clastic formation and that includes different values of density and viscosity for mud filtrate and formation hydrocarbon. These analyses provide evidence of the presence of a high-resistivity region near the borehole wall followed by a low-resistivity annulus close to the noninvaded resistivity region. Such an abnormal resistivity annulus is predominantly caused by high viscosity contrasts between mud filtrate and formation oil. The combined simulation of invasion and array-induction logs in the presence of OBM invasion provides a more reliable estimate of water saturation, which improves the assessment of in-place hydrocarbon reserves.
Development of a Data-Partition Technique for Gradient-Based Optimization Methods in History Matching
Authors: Ding D.Y.. Y.
Published: April 2011

Assisted history matching is now widely used to constrain reservoir models. However, history matching is a complex inverse problem, and it is always a big challenge to history match large fields with a large number of parameters.

In this paper, we present a new technique for the gradient-based optimization methods to improve history matching for large fields. This new technique is based on data partition for the gradient calculations. In history matching, the objective function can be split into local components, and a local component generally depends on fewer influential parameters. On the basis of this decomposition, we can propose a perturbation design, which allows us to calculate all derivatives of the objective function with only a few perturbations. This method is particularly interesting for regional and well-level history matching, and it is also suitable to match geostatistical models by introducing numerous local parameters. This new technique makes history matching with a large number of parameters (large field) tractable.
Reserves Overbooking: The Problem We Are Finally Going To Talk About
Authors: Olsen Grant T. , Lee W. John , Blasingame Thomas A.
Published: April 2011

Oil and gas reserves estimates that honor disclosure requirements of the US Securities and Exchange Commission (SEC) are critically important in the international oil and gas industry. Unfortunately, a number of exploration and production (E&P) companies have allegedly overstated and subsequently written down certain reserves volumes in recent years. In some cases, the consequences have been quite adverse. We document some of these cases of reserves overstatements and summarize the consequences. Reserves write downs are of obvious interest to numerous groups involved in the reserves estimation process and outcome, including estimators, managers, investors, creditors, and regulators. The magnitude and nature of recent overstatement cases, relative unfamiliarity with the SEC's inner workings, and the SEC's new reserves-reporting requirements increase the need to examine critically reserves disclosures and reserves overstatements.
Improving the SAGD Performance by Introducing a New Well Configuration
Authors: Mojarab Mohamad , Harding Thomas G. , Maini Brij B.
Published: April 2011

Steam-assisted gravity drainage (SAGD) is a commercially successful recovery process that produces heavy oils and bitumen. The method ensures both a stable displacement front of steam and economical rates by using gravity as the driving force with a pair of horizontal wells for injection/production. Although several ways of improving the performance have been discussed in the literature, the well configuration employed in the process has remained the same as originally proposed by Butler et al. (1981). A systematic attempt to improve the performance by using radically different well configurations has not been reported.

This paper presents a study intended to examine the applicability of a new well configuration to SAGD processes in Athabasca and Cold Lake reservoirs in central and northern Alberta. The fully implicit thermal-reservoir simulator, CMG's STARS 2007, with fully coupled wellbores was used to account for frictional pressure drop and heat losses along the wellbore. 3D numerical simulation models were set up, and sensitivity analyses were conducted on injection pressure. After optimization of the injection pressure, an investigation of new well configurations was conducted using these models. The result of this work shows that the SAGD-process performance in Athabasca and Cold Lake reservoirs can be improved significantly by changing the well configuration.