bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional Magnetic Resonance Imaging in Nursing Research
Authors: Johnson L. Clark , Richards Todd L. , Archbold Kristen H. , Landis Carol A.
Published: June 2006

Functional magnetic resonance imaging (fMRI) is a powerful noninvasive neuroimaging technique nurse scientists can use to investigate the structure and cognitive capacities of the brain. A strong magnetic field and intermittent high-frequency pulses cause protons in body tissues to release energy, which can be recorded and processed into images that are sensitive to specific tissue characteristics. Although temporal and spatial resolution constraints define an upper limit to the precision of magnetic resonance (MR) scanners, the primary index of neuronal activity, hemodynamic response, can be efficiently estimated. Characteristics of the experimental environment, the hypothesis of interest, and the physiology of the cognitive process under investigation provide guidance for the design and limit available options. The processing of functional data to remove unwanted variability is briefly described as are the techniques used to estimate statistical effects and control for the rate of false positives in the results. A detailed applied example of nursing research is included to demonstrate the practical application of the theory, methods, and techniques being discussed. A glossary of key terms is also provided.
Oral Health Measurement in Nursing Research: State of the Science
Authors: Munro Cindy L. , Grap Mary Jo , Jablonski Rita , Boyle Anne
Published: June 2006

Oral health can impact general health and systemic disease. Changes in dental plaque, oral microbial flora, and local oral immunity may be important in the development or exacerbation of disease in critically ill patients, trauma patients, adults with chronic obstructive pulmonary disease, and frail elderly. Inasmuch as oral health potentially can be influenced by nursing interventions, nursing research in this area can contribute greatly to improved patient outcomes in these diverse populations. The authors’ research teams have conducted several federally funded projects focused on oral health and have developed synergy in research methods. A unifying theme for these research projects is the measurement of oral health. Standardized measures of components of oral health are available and applicable across populations, and their uses and relationship to nursing research and patient outcomes will be discussed.
From Bedside to Bench and Back Again: Research Issues in Animal Models of Human Disease
Authors: Tkacs Nancy C. , Thompson Hilaire J.
Published: June 2006

To improve outcomes for patients with many serious clinical problems, multifactorial research approaches by nurse scientists, including the use of animal models, are necessary. Animal models serve as analogies for clinical problems seen in humans and must meet certain criteria, including validity and reliability, to be useful in moving research efforts forward. This article describes research considerations in the development of rodent models. As the standard of diabetes care evolves to emphasize intensive insulin therapy, rates of severe hypoglycemia are increasing among patients with type 1 and type 2 diabetes mellitus. A consequence of this change in clinical practice is an increase in rates of two hypoglycemia-related diabetes complications: hypoglycemia-associated autonomic failure (HAAF) and resulting hypoglycemia unawareness. Work on an animal model of HAAF is in an early developmental stage, with several labs reporting different approaches to model this complication of type 1 diabetes mellitus. This emerging model serves as an example illustrating how evaluation of validity and reliability is critically important at each stage of developing and testing animal models to support inquiry into human disease.
Detection of Cardiac Variability in the Isolated Rat Heart
Authors: Schumacher Autumn M. , Zbilut Joseph P. , Webber Charles L. , Schwertz Dorie W. , Piano Mariann R.
Published: June 2006

Cardiac variability can be assessed from two perspectives: beat-to-beat performance and continuous performance during the cardiac cycle. Linear analysis techniques assess cardiac variability by measuring the physical attributes of a signal, whereas nonlinear techniques evaluate signal dynamics. This study sought to determine if recurrence quantification analysis (RQA), a nonlinear technique, could detect pharmacologically induced autonomic changes in the continuous left ventricular pressure (LVP) and electrographic (EC) signals from an isolated rat heart—a model that theoretically contains no inherent variability. LVP and EC signal data were acquired simultaneously during Langendorff perfusion of isolated rat hearts before and after the addition of acetylcholine (n = 11), norepinephrine (n = 12), or no drug (n = 12). Two-minute segments of the continuous LVP and EC signal data were analyzed by RQA. Findings showed that%recurrence,%determinism, entropy, maxline, and trend from the continuous LVP signal significantly increased in the presence of both acetylcholine and norepinephrine, although systolic LVP significantly increased only with norepinephrine. In the continuous EC signal, the RQA trend variable significantly increased in the presence of norepinephrine. These results suggest that when either the sympathetic or parasympathetic division of the autonomic nervous system overwhelms the other, the dynamics underlying cardiac variability become stationary. This study also shows that information concerning inherent variability in the isolated rat heart can be gained via RQA of the continuous cardiac signal. Although speculative, RQA may be a tool for detecting alterations in cardiac variability and evaluating signal dynamics as a nonlinear indicator of cardiac pathology.
Simultaneous activation of multiple signal transduction pathways confers poor prognosis in acute myelogenous leukemia
Authors: Kornblau Steven M. , Womble Matthew , Qiu Yi Hua , Jackson C. Ellen , Chen Wenjing , Konopleva Marina , Estey Elihu H. , Andreeff Michael
Published: June 2006

Deregulation of signal transduction pathways (STPs) may promote leukemogenesis by conferring cell proliferation and survival advantages in acute myelogenous leukemia (AML). Several agents targeting STPs are under development; however, redundancy and cross-talk between STPs could activate multiple downstream effectors and this could negate the effect of single-target inhibition. The frequency of concurrent activation of multiple STPs in AML and the prognostic relevance of STP activation in AML are unknown. STP protein expression (PKCα, ERK2, pERK2, AKT, and pAKT) was measured by Western blot in samples from 188 patients with newly diagnosed, untreated AML. In univariate and multivariate analysis high levels of PKCα, ERK, pERK, and pAKT, but not AKT, were adverse factors for survival as was the combination variable PKCα-ERK2&pERK2-pAKT. Survival progressively decreased as the number of activated pathways increased. Patients were more likely to have none or all 3 pathways activated than was predicted based on the frequency of individual pathway activation, strongly suggesting that cross-activation occurred. Simultaneous activation of multiple STPs is common in AML and has a progressively worse adverse effect on prognosis. It is thus likely that only combinations of agents that target the multiply activated STPs will be beneficial for patients with AML.
Patterns of MADS-box gene expression mark flower-type development in Gerbera hybrida(Asteraceae)
Authors: Laitinen Roosa AE , Broholm Suvi , Albert Victor A , Teeri Teemu H , Elomaa Paula
Published: June 2006

Background

The inflorescence of the cut-flower crop Gerbera hybrida (Asteraceae) consists of two principal flower types, ray and disc, which form a tightly packed head, or capitulum. Despite great interest in plant morphological evolution and the tractability of the gerbera system, very little is known regarding genetic mechanisms involved in flower type specification. Here, we provide comparative staging of ray and disc flower development and microarray screening for differentially expressed genes, accomplished via microdissection of hundreds of coordinately developing flower primordia.

Results

Using a 9K gerbera cDNA microarray we identified a number of genes with putative specificity to individual flower types. Intrestingly, several of these encode homologs of MADS-box transcription factors otherwise known to regulate flower organ development. From these and previously obtained data, we hypothesize the functions and protein-protein interactions of several gerbera MADS-box factors.

Conclusion

Our RNA expression results suggest that flower-type specific MADS protein complexes may play a central role in differential development of ray and disc flowers across the gerbera capitulum, and that some commonality is shared with known protein functions in floral organ determination. These findings support the intriguing conjecture that the gerbera flowering head is more than a mere floral analog at the level of gene regulation.
Identification of multi-drug resistant Pseudomonas aeruginosa clinical isolates that are highly disruptive to the intestinal epithelial barrier
Authors: Zaborina Olga , Kohler Jonathan E , Wang Yingmin , Bethel Cindy , Shevchenko Olga , Wu Licheng , Turner Jerrold R , Alverdy John C
Published: June 2006

Background

Multi-drug resistant Pseudomonas aeruginosa nosocomial infections are increasingly recognized worldwide. In this study, we focused on the virulence of multi-drug resistant clinical strains P. aeruginosa against the intestinal epithelial barrier, since P. aeruginosa can cause lethal sepsis from within the intestinal tract of critically ill and immuno-compromised patients via mechanisms involving disruption of epithelial barrier function.

Methods

We screened consecutively isolated multi-drug resistant P. aeruginosa clinical strains for their ability to disrupt the integrity of human cultured intestinal epithelial cells (Caco-2) and correlated these finding to related virulence phenotypes such as adhesiveness, motility, biofilm formation, and cytotoxicity.

Results

Results demonstrated that the majority of the multi-drug resistant P. aeruginosa clinical strains were attenuated in their ability to disrupt the barrier function of cultured intestinal epithelial cells. Three distinct genotypes were found that displayed an extreme epithelial barrier-disrupting phenotype. These strains were characterized and found to harbor the exoU gene and to display high swimming motility and adhesiveness.

Conclusion

These data suggest that detailed phenotypic analysis of the behavior of multi-drug resistant P. aeruginosa against the intestinal epithelium has the potential to identify strains most likely to place patients at risk for lethal gut-derived sepsis. Surveillance of colonizing strains of P. aeruginosa in critically ill patients beyond antibiotic sensitivity is warranted.
Interactions between Nef and AIP1 proliferate multivesicular bodies and facilitate egress of HIV-1
Authors: Costa Luciana J , Chen Nan , Lopes Adriana , Aguiar Renato S , Tanuri Amilcar , Plemenitas Ana , Peterlin B Matija
Published: June 2006

Background

Nef is an accessory protein of primate lentiviruses, HIV-1, HIV-2 and SIV. Besides removing CD4 and MHC class I from the surface and activating cellular signaling cascades, Nef also binds GagPol during late stages of the viral replicative cycle. In this report, we investigated further the ability of Nef to facilitate the replication of HIV-1.

Results

To this end, first the release of new viral particles was much lower in the absence of Nef in a T cell line. Since the same results were obtained in the absence of the viral envelope using pseudo-typed viruses, this phenomenon was independent of CD4 and enhanced infectivity. Next, we found that Nef not only possesses a consensus motif for but also binds AIP1 in vitro and in vivo. AIP1 is the critical intermediate in the formation of multivesicular bodies (MVBs), which play an important role in the budding and release of viruses from infected cells. Indeed, Nef proliferated MVBs in cells, but only when its AIP1-binding site was intact. Finally, these functions of Nef were reproduced in primary macrophages, where the wild type but not mutant Nef proteins led to increased release of new viral particles from infected cells.

Conclusion

We conclude that by binding GagPol and AIP1, Nef not only proliferates MVBs but also contributes to the egress of viral particles from infected cells.
Transcriptional Regulation of Metabotropic Glutamate Receptor 2/3 Expression by the NF-κB Pathway in Primary Dorsal Root Ganglia Neurons: A Possible Mechanism for the Analgesic Effect of L-Acetylcarnitine
Authors: Chiechio Santina , Copani Agata , De Petris Laura , Morales Maria Elena P , Nicoletti Ferdinando , Gereau Robert W
Published: June 2006

L-acetylcarnitine (LAC), a drug utilized for the treatment of neuropathic pain in humans, has been shown to induce analgesia in rodents by up-regulating the expression of metabotropic glutamate receptor 2 (mGlu2) in dorsal root ganglia (DRG). We now report that LAC-induced upregulation of mGlu2 expression in DRG cultures involves transcriptional activation mediated by nuclear factor-kappaB (NF-κB). A single application of LAC (250 μM) to DRG cultures induced a transient increase in mGlu2 mRNA, which was observable after 1 hour and was no longer detectable after 1 to 4 days. In contrast, LAC treatment had no effect on mGlu3 mRNA expression. Pharmacological inhibition of NF-κB binding to DNA by caffeic acid phenethyl ester (CAPE) (2.5 μg/ml for 30 minutes) reduced the constitutive expression of mGlu2 and mGlu3 mRNA after 1–4 days and reduced the constitutive expression of mGlu2/3 protein at 4 days. This evidence combined with the expression of p65/RelA and c-Rel in DRG neurons indicated that expression of mGlu2 and mGlu3 is endogenously regulated by the NF-κB family of transcription factors. Consistent with this idea, the transient increase in mGlu2 mRNA induced by LAC after 1 hour was completely suppressed by CAPE. Furthermore, LAC induced an increase in the acetylation of p65/RelA, a process that enhances the transcriptional activity of p65/RelA. These results are consistent with the hypothesis that LAC selectively induces the expression of mGlu2 by acting as a donor of acetyl groups, thus enhancing the activity of the NF-κB family of transcription factors. Accordingly, we show that carnitine, which has no effect on pain thresholds, had no effect on p65/RelA acetylation and did not enhance mGlu2 expression. Taken together, these results demonstrate that expression of mGlu2 and mGlu3 mRNA is regulated by the NF-κB transcriptional machinery, and that agents that increase acetylation and activation of NF-κB transcription factors might induce analgesia via upregulation of mGlu2 in DRG neurons.
CHARITY: Cha gas car diomyopathy bi soprolol int ervention study: a randomized double-blind placebo force-titration controlled study with Bisoprolol in patients with chronic heart failure secondary to Chagas cardiomyopathy [NCT00323973]
Authors: Quiros Franklin R , Morillo Carlos A , Casas Juan P , Cubillos Luz A , Silva Federico A
Published: June 2006

Background

Chagas' disease is the major cause of disability secondary to tropical diseases in young adults from Latin America, and around 20 million people are currently infected byT. cruzi. Heart failure due to Chagas cardiomyopathy is the main clinical presenation in Colombia. Heart failure due to Chagas' disease may respond to digoxin, diuretics and vasodilator therapy. Beta-adrenoreceptor antagonism seems to protect against the increased risk of cardiac arrhythmia and sudden death due to chronic sympathetic stimulation. The aim of this study is to evaluate the effects of the selective beta-adrenergic receptor blocker Bisoprolol on cardiovascular mortality, hospital readmission due to progressive heart failure and functional status in patients with heart failure secondary to Chagas' cardiomyopathy.

Methods/design

A cohort of 500T. cruziseropositive patients (250 per arm) will be selected from several institutions in Colombia. During the pretreatment period an initial evaluation visit will be scheduled in which participants will sign consent forms and baseline measurements and tests will be conducted including blood pressure measurements, twelve-lead ECG and left ventricular ejection fraction assessment by 2D echocardiography. Quality of life questionnaire will be performed two weeks apart during baseline examination using the "Minnesota living with heart failure" questionnaire. A minimum of two 6 minutes corridor walk test once a week over a two-week period will be performed to measure functional class. During the treatment period patients will be randomly assigned to receive Bisoprolol or placebo, initially taking a total daily dose of 2.5 mgrs qd. The dose will be increased every two weeks to 5, 7.5 and 10 mgrs qd (maximum maintenance dose). Follow-up assessment will include clinical check-up, and blood collection for future measurements of inflammatory reactants and markers. Quality of life measurements will be obtained at six months. This study will allow us to explore the effect of beta-blockers in chagas' cardiomyopathy.
The effect of open lung ventilation on right ventricular and left ventricular function in lung-lavaged pigs
Authors: Reis Miranda Dinis , Klompe Lennart , Cademartiri Filippo , Haitsma Jack J , Palumbo Alessandro , Takkenberg Johanna JM , Lachmann Burkhard , Bogers Ad JJC , Gommers Diederik
Published: June 2006

Introduction

Ventilation according to the open lung concept (OLC) consists of recruitment maneuvers, followed by low tidal volume and high positive end-expiratory pressure, aiming at minimizing atelectasis. The minimization of atelectasis reduces the right ventricular (RV) afterload, but the increased intrathoracic pressures used by OLC ventilation could increase the RV afterload. We hypothesize that when atelectasis is minimized by OLC ventilation, cardiac function is not affected despite the higher mean airway pressure.

Methods

After repeated lung lavage, each pig (n = 10) was conventionally ventilated and was ventilated according to OLC in a randomized cross-over setting. Conventional mechanical ventilation (CMV) consisted of volume-controlled ventilation with 5 cmH2O positive end-expiratory pressure and a tidal volume of 8–10 ml/kg. No recruitment maneuvers were performed. During OLC ventilation, recruitment maneuvers were applied until PaO2/FiO2 > 60 kPa. The peak inspiratory pressure was set to obtain a tidal volume of 6–8 ml/kg. The cardiac output (CO), the RV preload, the contractility and the afterload were measured with a volumetric pulmonary artery catheter. A high-resolution computed tomography scan measured the whole lung density and left ventricular (LV) volumes.

Results

The RV end-systolic pressure–volume relationship, representing RV afterload, during steady-state OLC ventilation (2.7 ± 1.2 mmHg/ml) was not significantly different compared with CMV (3.6 ± 2.5 mmHg/ml). Pulmonary vascular resistance (OLC, 137 ± 49 dynes/s/cm5 versus CMV, 130 ± 34 dynes/s/cm5) was comparable between groups. OLC led to a significantly lower amount of atelectasis (13 ± 2% of the lung area) compared with CMV (52 ± 3% of the lung area). Atelectasis was not correlated with pulmonary vascular resistance or end-systolic pressure–volume relationship.

The LV contractility and afterload during OLC was not significantly different compared with CMV. Compared with baseline, the LV end-diastolic volume (66 ± 4 ml) decreased significantly during OLC (56 ± 5 ml) ventilation and not during CMV (61 ± 3 ml). Also, CO was significantly lower during OLC ventilation (OLC, 4.1 ± 0.3 l/minute versus CMV, 4.9 ± 0.3 l/minute).

Conclusion

In this experimental study, OLC resulted in significantly improved lung aeration. Despite the use of elevated airway pressures, no evidence was found for a negative effect of OLC on RV afterload or LV afterload, which might be associated with a loss of hypoxic pulmonary vasoconstriction due to alveolar recruitment. The reductions in the CO and in the mean pulmonary artery pressure were consequences of a reduced preload.
Slow, stochastic transgene repression with properties of a timer
Authors: Wang Clifford L , Yang Desirée C , Wabl Matthias
Published: June 2006

Background

When gene expression varies unpredictably between genetically identical organisms, this is sometimes ascribed as stochastic. With the prevalence of retroviral vectors, stochastic repression is often observed and can complicate the interpretation of outcomes. But it may also faithfully reflect characteristics of sites in the genome.

Results

We created and identified several cell clones in which, within a given cell, retroviral transcription of a transgene was repressed heritably and essentially irreversibly. This repression was relatively slow; total repression in all cells took months. We observed the dynamics of repression and found that they were ergodic, that is, tending with a probability to a final state independent of previous conditions. Different positions of the transgene in the genome demonstrated different dynamics. At a position on mouse chromosome 9, repression abided by near perfect first-order kinetics and was highly reproducible, even under conditions where the number of cell generations per day varied.

Conclusion

We propose that such a cell division independent 'off' mechanism could play a role in endogenous gene expression, potentially providing an epigenetically based timer for extended periods.
Measuring gravity on ice: An example from Wanapitei Lake, Ontario, Canada
Authors: Ugalde Hernan A. , L’Heureux Elizabeth , Lachapelle Richard , Milkereit Bernd
Published: June 2006

Large lakes have always represented a problem for regional gravity databases; the difficulty of access means gaps or coarse spacing in the sampling. Satellite, airborne, and shipborne gravity techniques are options, but the resolution and/or cost of these systems make them impractical or inaccurate for exploration or environmental studies, where the required resolution is [Formula: see text]. In this study, the feasibility of a ground gravity survey over a frozen lake where ice moves because of windy conditions is assessed. Lake Wanapitei, widely accepted as resulting from the impact of a meteorite 37 million years ago, is one of these cases in which the necessity of expanding coverage over poorly sampled regions arose from a significant gap between surface and airborne geophysical maps. Two gravity surveys were completed on the ice of Lake Wanapitei in the winters of 2003 and 2004. To study the structure, longtime series of gravity field measurements were recorded for 98 stations, allowing for improved control over the noise sources in the data. Final processing and integration with an existing regional data set in the area and the application of terrain corrections reduced the amplitude of the circular anomaly from 15 to [Formula: see text] and its diameter from 11 to [Formula: see text]. The feasibility of gravity surveys on ice was assessed, and we determined that for large-scale studies such as this one, the quality of the data, even under noisy conditions, was acceptable. However, for more detailed mapping, calm wind conditions and long time series are required.
Highly accurate absorbing boundary conditions for wide-angle wave equations
Authors: Heidari A. Homayoun , Guddati Murthy N.
Published: June 2006

We develop a new class of absorbing boundary conditions (ABCs) to prevent unwanted artifacts and wraparounds associated with aperture truncation in migration/modeling using high-order, one-way wave equations. The fundamental approach behind the proposed development is the efficient discretization of the half-space, beyond the boundary of interest, using midpoint-integrated imaginary finite elements, an idea recently utilized in the development of effective one-way wave equations. The proposed absorbing boundary conditions essentially add absorbing layers at the aperture truncation points. We derive the absorbing boundary conditions, analyze their properties, and develop a stable explicit finite-difference scheme to solve the downward-continuation problem modified by these boundary conditions. With the help of numerical examples, we conclude that with as few as three absorbing layers, i.e., two additional gridpoints, the waves can be absorbed completely, thus preventing associated artifacts.
Integration of diverse physical-property models: Subsurface zonation and petrophysical parameter estimation based on fuzzy c -means cluster analyses
Authors: Paasche Hendrik , Tronicke Jens , Holliger Klaus , Green Alan G. , Maurer Hansruedi
Published: June 2006

Inversions of an individual geophysical data set can be highly nonunique, and it is generally difficult to determine petrophysical parameters from geophysical data. We show that both issues can be addressed by adopting a statistical multiparameter approach that requires the acquisition, processing, and separate inversion of two or more types of geophysical data. To combine information contained in the physical-property models that result from inverting the individual data sets and to estimate the spatial distribution of petrophysical parameters in regions where they are known at only a few locations, we demonstrate the potential of the fuzzy [Formula: see text]-means (FCM) clustering technique. After testing this new approach on synthetic data, we apply it to limited crosshole georadar, crosshole seismic, gamma-log, and slug-test data acquired within a shallow alluvial aquifer. The derived multiparameter model effectively outlines the major sedimentary units observed in numerous boreholes and provides plausible estimates for the spatial distributions of gamma-ray emitters and hydraulic conductivity.
Direct reservoir parameter estimation using joint inversion of marine seismic AVA and CSEM data
Authors: Hoversten G. Michael , Cassassuce Florence , Gasperikova Erika , Newman Gregory A. , Chen Jinsong , Rubin Yoram , Hou Zhangshuan , Vasco Don
Published: June 2006

Accurately estimating reservoir parameters from geophysical data is vitally important in hydrocarbon exploration and production. We have developed a new joint-inversion algorithm to estimate reservoir parameters directly, using both seismic amplitude variation with angle of incidence (AVA) data and marine controlled-source electromagnetic (CSEM) data. Reservoir parameters are linked to geophysical parameters through a rock-properties model. Errors in the parameters of the rock-properties model introduce errors of comparable size in the reservoir-parameter estimates produced by joint inversion. Tests of joint inversion on synthetic 1D models demonstrate improved fluid saturation and porosity estimates for joint AVA-CSEM data inversion (compared with estimates from AVA or CSEM inversion alone). A comparison of inversions of AVA data, CSEM data, and joint AVA-CSEM data over the North Sea Troll field, at a location for which we have well control, shows that the joint inversion produces estimates of gas saturation, oil saturation, and porosity that are closest (as measured by the rms difference, the [Formula: see text] norm of the difference, and net values over the interval) to the logged values. However, CSEM-only inversion provides the closest estimates of water saturation.
Ground-penetrating radar theory and application of thin-bed offset-dependent reflectivity
Authors: Bradford John H. , Deeds Jacob C.
Published: June 2006

Offset-dependent reflectivity or amplitude-variation-with-offset (AVO) analysis of ground-penetrating radar (GPR) data may improve the resolution of subsurface dielectric permittivity estimates. A horizontally stratified medium has a limiting layer thickness below which thin-bed AVO analysis is necessary. For a typical GPR signal, this limit is approximately 0.75 of the characteristic wavelength of the signal. Our approach to modeling the GPR thin-bed response is a broadband, frequency-dependent computation that utilizes an analytical solution to the three-interface reflectivity and is easy to implement for either transverse electric (TE) or transverse magnetic (TM) polarizations. The AVO curves for TE and TM modes differ significantly. In some cases, constraining the interpretation using both TE and TM data is critical. In two field examples taken from contaminated-site characterization data, we find quantitative thin-bed modeling agrees with the GPR field data and available characterization data.
Multiconfiguration GPR measurements for geometric fracture characterization in limestone cliffs (Alps)
Authors: Jeannin Mathieu , Garambois Stéphane , Grégoire Colette , Jongmans Denis
Published: June 2006

Rock-mass fracturing is a key parameter in rock-fall hazard assessment. However, traditional geologic observations can provide information only about discontinuities at the surface. In this case study, detailed ground-penetrating-radar (GPR) measurements (with antennas of [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]) were conducted on a test site, using different acquisition configurations deployed on vertical cliff faces. Conventional 2D profile data, common-midpoint (CMP) survey data, and transmission data were acquired to evaluate the potential use of radar waves to characterize the geometry and properties of the major discontinuities (fractures) within a Mesozoic limestone massif. Results showed that the continuity and geometry (orientation and dip) of the major observed fractures, which are crucial parameters for assessing rock stability, can be obtained by combining vertical and horizontal profiles measured along the cliff. We used [Formula: see text] antennae and reached a maximum penetration of [Formula: see text], which limits the technique to rock volumes of a few tens of thousands of cubic meters. We observed significant differences in reflectivity along the detected fractures, which suggests that the fractures’ characteristics vary in the rock mass. We used transmission data to obtain a radar velocity image. Although the results were consistent with radar profiles on the cliff, they showed that the technique has little utility, beyond that of more traditional GPR methods, for delineating fractures in a rock mass.
Reflectivity modeling of a ground-penetrating-radar profile of a saturated fluvial formation
Authors: Clement William P. , Barrash Warren , Knoll Michael D.
Published: June 2006

Major horizons in radar reflection profiles may correlate with contacts between stratigraphic units or with structural breaks such as fault surfaces. Minor reflections may be caused by clutter or, in some cases, may indicate material properties or structure within stratigraphic units. In this study, we examine the physical basis for major and minor reflections observed in a shallow, unconfined, fluvial aquifer near Boise, Idaho, U. S. A. We compare a 2D profile from a surface ground-penetrating-radar reflection transect with the 1D modeled reflection profiles at three wells adjacent to the surface-reflection profile. The 1D models are based on dielectric constant and electrical conductivity values from borehole logs and vertical radar profile data. Reflections at the water table/capillary fringe, at the base of a sand-filled channel, and at the base of two sand-rich lenses in a cobble-dominated unit are recognizable in the surface-reflection profile and in all 1D reflectivity models. Less prominent reflections in stratigraphic units occur in both the surface-profile model and the reflectivity model. Although such minor reflections are not correlated easily, general similarities in their presence and location indicate that sometimes the reflections may be useful for recognizing internal facies structure or character.
Investigating the stratigraphy of an alluvial aquifer using crosswell seismic traveltime tomography
Authors: Moret Geoff J. , Knoll Michael D. , Barrash Warren , Clement William P.
Published: June 2006

In this study, we investigate the use of crosswell P-wave seismic tomography to obtain spatially extensive information about subsurface sedimentary architecture and heterogeneity in alluvial aquifers. Our field site was a research wellfield in an unconfined aquifer near Boise, Idaho. The aquifer consists of a ∼ 20-m-thick sequence of alluvial cobble-and-sand deposits, which have been subdivided into five stratigraphic units based on neutron porosity logs, grain-size analysis, and radar reflection data. We collected crosswell and borehole-to-surface seismic data in wells [Formula: see text] apart. We carefully considered the impact of well deviation, data quality control, and the choice of inversion parameters. Our linearized inverse routine had a curved-ray forward model and used different grids for forward modeling and inversion. An analysis of the model covariance and resolution matrices showed that the velocity models had an uncertainty of [Formula: see text], a vertical resolution of [Formula: see text], and a horizontal resolution of [Formula: see text]. The velocity in the saturated zone varied between [Formula: see text] and [Formula: see text]. Inclusion of the borehole-to-surface data eliminated the X- shaped pattern that is a common artifact in crosswell tomography, and the increased angular coverage also improved the accuracy of the model near the top of the tomogram. The final velocity model is consistent with previous stratigraphic analyses of the site, although the locations of some of the unit boundaries differ by as much as [Formula: see text] in places. The results of this study demonstrate that seismic tomography can be used to image the sedimentary architecture of unconsolidated alluvial aquifers, even when the lithologic contrasts between units are subtle.
Quantifying total sulfide content of cores and cut-rock surfaces using thermal infrared reflectance
Authors: Feng Jilu , Rivard Benoit , Gallie E. Ann , Sanchez Arturo
Published: June 2006

In this study, core samples of sulfide-rich zones were delineated from their host rock and a quantitative estimation of sulfide content on cut-rock faces was made using thermal infrared reflectance (TIR; [Formula: see text] region) spectroscopy. Core sections and rocks were collected from mines in the Sudbury basin, Ontario, Canada. The TSC% (areal percentage of total sulfide content) of each sample was then estimated by summing the modal abundance of all sulfide minerals (chalcopyrite, pyrrhotite, and pentlandite). TIR at [Formula: see text] [Formula: see text] is linearly related to TSC%. The average of the spectral ratios [Formula: see text] and [Formula: see text] [Formula: see text] is related exponentially to TSC%. The coefficients of determination [Formula: see text] based on a calibration data set are 0.90 and 0.87, respectively. Two models were tested, the [Formula: see text] model and the [Formula: see text] model; the latter combines [Formula: see text] and [Formula: see text]. The value for [Formula: see text] for predicted TSC% versus observed TSC% (from thin sections) is 0.98 and 0.97, respectively, with little or no bias. The standard deviation of the residuals is 3.1 and 3.5 TSC%, respectively. The [Formula: see text] model is preferred over the [Formula: see text] model because it is linear and therefore does not have the problem with insensitivity at low TSC% that the exponential [Formula: see text] model has. In addition, from the viewpoint of developing an instrument for automated core logging, the [Formula: see text] model requires measurements at only one wavelength rather than three and hence requires a less expensive instrument.
Model parameters of the nonlinear stiffness of the vibrator-ground contact determined by inversion of vibrator accelerometer data
Authors: Lebedev Andrey V. , Beresnev Igor A. , Vermeer Pieter L.
Published: June 2006

Analysis of vibroseis data shows that harmonic distortion in the ground-force signal may exceed the primary distortions in the hydraulic system. This can be explained by the baseplate-ground contact nonlinearity created by the deformations of the contact roughness. We separated the nonlinear distortion generated in the hydraulics from that generated at the contact. We then formulated an inverse problem for resolving the parameters of the nonlinear contact rigidity, based on the equivalent model of the nonlinear source and the comparison of predicted and observed harmonic levels. The inverse problem was solved for models of bilinear contact and the contact with the rigidity smoothly varying between two asymptotic values, using data obtained on sandy soil. Rigidities changing between approximately [Formula: see text] in compression and [Formula: see text] in tension were resolved from the inversion for both models, although the smooth nonlinear-rigidity model is a better approximation. The analysis shows the adequacy of the equivalent mechanical source model used for the description of nolinear distortions in real soil-baseplate coupled systems.
Bayesian time-lapse inversion
Authors: Buland Arild , El Ouair Youness
Published: June 2006

A new, fast inversion approach for time-lapse seismic data is developed where the uncertainty of the inversion results is an integral part of the solution. The inversion method estimates changes in the elastic material properties of a reservoir because of production of hydrocarbons, including uncertainty bounds on these estimates. The changes in elastic properties then can be related to changes in hydrocarbon saturation and reservoir pressure by using rock-physics relations. The inversion operates directly on the difference between a repeat survey and a baseline survey. This is advantageous with respect to the uncertainty calculation, because an estimate of the seismic uncertainty can be obtained directly from the difference data in zones not affected by production. The method is formulated in a Bayesian setting, and the solution is represented by explicit expressions for the posterior expectation and the covariance of the elastic parameter changes. The explicit analytical form of the posterior distribution provides a computationally fast inversion method. Results of the applied approach to a real data set from the Norne field are consistent with the expected effects of water flushing because of water injection.
AVO attribute inversion for finely layered reservoirs
Authors: Stovas Alexey , Landrø Martin , Avseth Per
Published: June 2006

Assuming that a turbidite reservoir can be approximated by a stack of thin shale-sand layers, we use standard amplitude variaiton with offset (AVO) attributes to estimate net-to-gross (N/G) and oil saturation. Necessary input is Gassmann rock-physics properties for sand and shale, as well as the fluid properties for hydrocarbons. Required seismic input is AVO intercept and gradient. The method is based upon thin-layer reflectivity modeling. It is shown that random variability in thickness and seismic properties of the thin sand and shale layers does not change significantly the AVO attributes at the top and base of the turbidite-reservoir sequence. The method is tested on seismic data from offshore Brazil. The results show reasonable agreement between estimated and observed N/G and oil saturation. The methodology can be developed further for estimating changes in pay thickness from time-lapse seismic data.
Effective elasticity of rocks with closely spaced and intersecting cracks
Authors: Grechka Vladimir , Kachanov Mark
Published: June 2006

The noninteraction approximation (NIA) is the simplest effective media theory that describes the overall elasticity of fractured rocks. If the NIA is used for fracture characterization, its accuracy and the range of applicability must be estimated. We do it by performing a series of 3D finite element simulations of effective elasticity for models that contain several sets of fractures embedded in otherwise isotropic host rock. We intentionally place the cracks close to each other to create strong interactions in their local stress fields. In addition, we allow the cracks to intersect in such a way that they do not break a rock specimen apart.

Perhaps surprisingly, we find that fracture interactions and intersections have little influence on the effective elasticity, and the NIA performs well in all cases. While it has a tendency to slightly underestimate the effective stiffnesses, the incurred errors are small; their typical magnitudes are just a few percent in the entire range of the crack densities expected in naturally fractured formations. In our view, this makes the noninteraction approximation the method of choice for fracture characterization.
Attenuation and dispersion of P-waves in porous rocks with planar fractures: Comparison of theory and numerical simulations
Authors: Lambert Gracjan , Gurevich Boris , Brajanovski Miroslav
Published: June 2006

To explore the validity and limitations of the theoretical model of wave propagation in porous rocks with periodic distribution of planar fractures, we perform numerical simulation using a poroelastic reflectivity algorithm. The numerical results are found to be in good agreement with the analytical model, not only for periodic fractures, but also for random distribution of constant thickness fractures.
3D wavefield extrapolation with optimum split-step Fourier method
Authors: Liu Linong , Zhang Jianfeng
Published: June 2006

A one-way propagator is proposed for more accurately modeling wide-angle wavefields in the presence of severe lateral variations of the velocity. The method adds a higher-order correction to improve the split-step Fourier method by directly designing a cascaded operator that matches the exact phase-shift operator of a varying velocity. Using an optimization scheme, the coefficients in the cascaded operator are determined according to the local velocity distribution and the prescribed angular range of wavefield propagation. The proposed algorithm is implemented alternately in spatial and wavenumber domains using fast Fourier transforms, as in the split-step Fourier and generalized-screen methods. This algorithm can achieve higher accuracy than the generalized-screen method for wide-angle wavefields, although the same numerical scheme is used with comparable computational cost. No extra error arises for the proposed algorithm when used for 3D wave propagation, in contrast to methods that introduce an implicit finite–difference higher-order correction to the split-step Fourier method, such as the Fourier finite difference (FFD) and wide-angle screen methods. A detailed comparison of the proposed one-way propagator with the split-step Fourier, generalized-screen, and FFD methods is presented. The 2D Marmousi and 3D SEG/EAEG overthrust data sets are used to test the prestack depth-migration schemes developed based on the proposed one-way propagators.
Human Chorionic Gonadotropin-Dependent Up-Regulation of Genes Responsible for Estrogen Sulfoconjugation and Export in Granulosa Cells of Luteinizing Preovulatory Follicles
Authors: Brown Kristy A. , Doré Monique , Lussier Jacques G. , Sirois Jean
Published: June 2006

Estrogen sulfotransferase (EST) is responsible for the sulfoconjugation of estrogens, thereby changing their physical properties and preventing their action via the estrogen receptors. These sulfoconjugated steroids no longer diffuse freely across the lipid bilayer; instead, they are exported by members of the ATP-binding cassette family, such as ABCC1. The objective of this study was to investigate the regulation of EST and ABCC1 during human chorionic gonadotropin (hCG)-induced ovulation/luteinization. The transcripts for EST and ABCC1 were cloned by RT-PCR, and the regulation of their mRNAs was studied in preovulatory follicles obtained during estrus at 0, 12, 24, 30, 33, 36, and 39 h after hCG. Results obtained from RT-PCR/Southern blot analyses showed significant changes in steady-state levels of both EST and ABCC1 mRNA after hCG treatment (P < 0.05). In granulosa cells, a significant increase in EST transcript was observed 30–39 h after hCG. Similarly, ABCC1 transcript levels were induced in granulosa cells 12–39 h after hCG. In contrast, no significant changes in either EST or ABCC1 were detected in theca interna samples after hCG. The increase in EST and ABCC1 transcripts observed in granulosa cells was reflected in preparations of intact follicle walls, suggesting that the granulosa cell layer contributes the majority of EST and ABCC1 expression in preovulatory follicles. The present study demonstrates that follicular luteinization is accompanied not only by a decrease in 17β-estradiol biosynthesis but also by an increase in expression of genes responsible for estrogen inactivation and elimination from granulosa cells, such as EST and ABCC1, respectively.
Progesterone Receptors (PR)-B and -A Regulate Transcription by Different Mechanisms: AF-3 Exerts Regulatory Control over Coactivator Binding to PR-B
Authors: Tung Lin , Abdel-Hafiz Hany , Shen Tianjie , Harvell Djuana M. E. , Nitao Lisa K. , Richer Jennifer K. , Sartorius Carol A. , Takimoto Glenn S. , Horwitz Kathryn B.
Published: June 2006

The two, nearly identical, isoforms of human progesterone receptors (PR), PR-B and -A, share activation functions (AF) 1 and 2, yet they possess markedly different transcriptional profiles, with PR-B being much stronger transactivators. Their differences map to a unique AF3 in the B-upstream segment (BUS), at the far N terminus of PR-B, which is missing in PR-A. Combined mutation of two LXXLL motifs plus tryptophan 140 in BUS, to yield PR-BdL140, completely destroys PR-B activity, because strong AF3 synergism with downstream AF1 and AF2 is eliminated. This synergism involves cooperative interactions among receptor multimers bound at tandem hormone response elements and is transferable to AFs of other nuclear receptors. Other PR-B functions—N-/C-terminal interactions, steroid receptor coactivator-1 coactivation, ligand-dependent down-regulation—also require an intact BUS. All three are autonomous in PR-A, and map to N-terminal regions common to both PR. This suggests that the N-terminal structure adopted by the two PR is different, and that for PR-B, this is controlled by BUS. Indeed, gene expression profiling of breast cancer cells stably expressing PR-B, PR-BdL140, or PR-A shows that mutation of AF3 destroys PR-B-dependent gene transcription without converting PR-B into PR-A. In sum, AF3 in BUS plays a critical modulatory role in PR-B, and in doing so, defines a mechanism for PR-B function that is fundamentally distinct from that of PR-A.
TGF-β1, TGF-β2, and TGF-β3 Exhibit Distinct Patterns of Expression During Cranial Suture Formation and Obliteration In Vivo and In Vitro
Authors: Opperman Lynne A. , Nolen Amber A. , Ogle Roy C.
Published: June 2006

Cranial sutures function as bone growth centers while themselves remaining unossified. Rat frontonasal sutures become obliterated by neonatal day 21 (N21), while coronal sutures do not fuse over the life of the animal. Coronal sutures induced to undergo osseous obliteration in vitro after removal of the dura mater were found to require soluble, heparin-binding factors present in dura mater to resist osseous obliteration. Transforming growth factor β1 (TGF-β1), β2, and β3, heparin-binding factors known to regulate bone cell proliferation and differentiation, were considered likely candidates. The presence and distribution of these factors in calvarial tissues both in vivo and in vitro were established by immunohistochemical analysis, while reverse transcription followed by polymerase chain reaction (RT/PCR) was employed to determine the presence of transcripts for these factors in mRNA isolated from microdissected dura mater. Results indicated that the presence of TGF-β1 and TGF-β2 were associated with developing coronal and frontonasal sutures, and that the continued presence of these factors was associated with osseous obliteration of the frontonasal suture. However, increased TGF-β3 immunoreactivity was associated with the coronal suture remaining unossified. RT/PCR demonstrated the presence of transcripts for TGF-β1, β2, and β3 in dural tissues isolated from rat calvaria. These data support the notion of a role for TGF-βs in regulating cranial suture morphogenesis and establish the in vitro model as a valid system for examining mechanisms by which growth factors regulate both suture morphogenesis and bone growth at the suture site.