bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence of electrical anisotropy in limestone formations using the RMT technique
Authors: Linde Niklas , Pedersen Laust B. 
Published: July 2004

Azimuthal resistivity surveys are often applied to complement hydrological information or to improve the location of observation boreholes in pump tests. Symmetric electrode configurations cannot distinguish anisotropy from lateral changes or dipping layers, but asymmetric arrays (e.g., the offset Wenner array) can. Tensor radiomagnetotellurics (RMT) is presented as an alternative method in studies of electrical anisotropy in the shallow subsurface. The electromagnetic and geomagnetic transfer functions provide information about the dimensionality of the data. These transfer functions can also be used to find the directions of anisotropy. Data with an anisotropic signature can be inverted for a one‐dimensional (1D) azimuthal anisotropy model. The method is faster than the azimuthal resistivity method. A 380‐m‐long profile of tensor RMT data (12.7–243 kHz) from limestones that overlie shale on the island of Gotland, Sweden, is used to show the merits of the method. The data have a clear anisotropic signature. The data are inverted for a three‐layer 1D model with azimuthal anisotropy using two different approaches: (1) a moving median filter of five neighboring stations and neglecting static shift parameters; and (2) treating each station separately and including static shifts of the electric field in the inversion. Both inversions show models having a marked anisotropy with anisotropy factors of 3.7 and 4.5, respectively, in the limestones. The second approach has a significantly better data fit. However, the first approach is preferred because the models are smoother from station to station.
Automatic determination of the magnetization–density ratio and magnetization inclination from the joint interpretation of 2D gravity and magnetic anomalies
Authors: Mendonça Carlos Alberto 
Published: July 2004

The Poisson theorem establishes a linear relationship between the gravity and magnetic potentials arising from common dense and magnetized bodies with constant magnetization–density ratio and magnetization direction. For geological formations satisfying such constraints (i.e., the Poisson conditions), this theorem provides suitable relationships between the gravity and magnetic anomalies that are useful in interpreting the related data sets. In such applications, both magnetization–density ratio (MDR) and magnetization direction can be estimated, thus helping the subsurface geological mapping from potential field data acquired on the earth's surface. However, no existing method is fully automatic, which has hampered extensive use in routine applications. Such a drawback follows the adoption of equations that, although obeying the Poisson theorem, relate particular components of the gravity and magnetic fields, thus requiring either a known magnetization direction or the implementation of iterative procedures to determine it.To allow one‐pass estimates for both MDR and magnetization direction (more precisely, its inclination projected on the plane normal to the source strike), this paper presents simple analytical solutions for these parameters by relating suitable gravity and magnetic vector fields that are derived from the gravity and magnetic data sets. Because current geophysical surveys usually provide only a single‐field component, a data processing scheme is developed to determine the required components in evaluating the desired vector fields. This is done by applying suitable linear transformations on the measured components according to well‐established filtering techniques in processing gravity and magnetic data. Except for distortions from noise, the proposed method automatically determines the MDR and the projected magnetization inclination for the underlying rocks everywhere the Poisson conditions are satisfied. Two‐dimensional sources are assumed, but no constraint upon their depth and cross‐section shape is required. Distorted estimates only appear close to the sources where at least one of the Poisson conditions is violated. In this case, the proposed technique furnishes apparent values for the rock properties. The abrupt changes of apparent values over contacts detect edges, thus facilitating the mapping of geological boundaries.The proposed technique is used to interpret two profiles across the Appalachian fold belt from the eastern portion of the State of Georgia, and the results are compared with some of the geological information available for the area.
Texture model regression for effective feature discrimination: Application to seismic facies visualization and interpretation
Authors: Gao Dengliang 
Published: July 2004

The classical approach to feature discrimination requires extraction and classification of multiple attributes. Such an approach is expensive in terms of computational time and storage space, and the results are generally difficult to interpret. With increasing data size and dimensionality, along with demand for high performance and productivity, the effectiveness of a feature‐discrimination methodology has become a critically important issue in many areas of science. To address such an issue, I developed a texture model regression (TMR) methodology. Unlike classical attribute extraction and classification algorithms, the TMR methodology uses an interpreter‐defined texture model as a calibrating filter and regresses the model texture with the data texture at each sample location to create a regression‐gradient volume. The new approach not only dramatically reduces computational cycle time and space but also creates betters results than those obtained from classical techniques, resulting in improved feature discrimination, visualization, and interpretation.Application of the TMR concept to reflection seismic data demonstrates its value in seismic‐facies analysis. In order to characterize reflection seismic images composed of wiggle traces with variable amplitude, frequency, and phase, I introduced two simple seismic‐texture models in this application. The first model is defined by a full cycle of a cosine function whose amplitude and frequency are the maximum amplitude and dominant frequency of wiggle traces in the interval of interest. The second model is defined by a specific reflection pattern known to be associated with a geologic feature of interest, such as gas sand in a hydrocarbon reservoir. I applied both models to a submarine turbidite system offshore West Africa and to a gas field in the deep‐water Gulf of Mexico, respectively. Based on extensive experimentation and comparative analysis, I found that the TMR process with such simple texture models creates superior results, using minimal computational resources. The result is geologically intriguing, easily interpretable, and consistent with general depositional and reservoir‐facies concepts. Such a successful application may be attributable to the sensitivity of image texture to physical texture in the Fresnel zone at an acoustic interface and therefore to lithology, depositional facies, and hydrocarbonsaturation.
Stochastic reservoir characterization using prestack seismic data
Authors: Eidsvik Jo , Avseth Per , Omre Henning , Mukerji Tapan , Mavko Gary 
Published: July 2004

Reservoir characterization must be based on information from various sources. Well observations, seismic reflection times, and seismic amplitude versus offset (AVO) attributes are integrated in this study to predict the distribution of the reservoir variables, i.e., facies and fluid filling. The prediction problem is cast in a Bayesian setting. The a priori model includes spatial coupling through Markov random field assumptions and intervariable dependencies through nonlinear relations based on rock physics theory, including Gassmann's relation. The likelihood model relating observations to reservoir variables (including lithology facies and pore fluids) is based on approximations to Zoeppritz equations. The model assumptions are summarized in a Bayesian network illustrating the dependencies between the reservoir variables. The posterior model for the reservoir variables conditioned on the available observations is defined by the a priori and likelihood models. This posterior model is not analytically tractable but can be explored by Markov chain Monte Carlo (MCMC) sampling. Realizations of reservoir variables from the posterior model are used to predict the facies and fluid‐filling distribution in the reservoir. A maximum a posteriori (MAP) criterion is used in this study to predict facies and pore‐fluid distributions. The realizations are also used to present probability maps for the favorable (sand, oil) occurrence in the reservoir. Finally, the impact of seismic AVO attributes—AVO gradient, in particular—is studied.The approach is demonstrated on real data from a turbidite sedimentary system in the North Sea. AVO attributes on the interface between reservoir and cap rock are extracted from 3D seismic AVO data. The AVO gradient is shown to be valuable in reducing the ambiguity between facies and fluids in the prediction.
Design of one‐way wavefield extrapolation operators, using smooth functions in WLSQ optimization
Authors: Thorbecke Jan W , Wapenaar Kees , Swinnen Gerd 
Published: July 2004

Many depth migration methods use one‐way frequency–space depth extrapolation methods. These methods are generally considered to be expensive, so it is important to find the most efficient way of implementing them. This usually means making spatial convolution operators that are as short as possible. Applying the extrapolation operators in a recursive way, using small depth steps, also demands that the operators do not amplify the wavefield at every depth step.Weighted least squares is an appropriate method to use for designing extrapolation operators that are accurate and efficient and that remain stable in a recursive algorithm. The extrapolated wavefields calculated with these operators are comparable with the extrapolation results obtained with other known operator design techniques as the Remez exchange method and nonlinear optimization. In this paper, the weighted least‐squares technique is refined by using different model functions. By smoothing the phase and amplitude transition at the evanescent cutoff, we can stabilize the resulting operators.The accuracy of the operators is shown in zero‐offset migration impulse responses in 2D and 3D media. The Sigsbee2A data set is used to illustrate the quality of the extrapolation operators in prestack depth migration in a complex medium.
Evidence that Cocaine- and Amphetamine-Regulated Transcript Is a Novel Intraovarian Regulator of Follicular Atresia
Authors: Kobayashi Yasuhiro , Jimenez-Krassel Fermin , Li Qinglei , Yao Jianbo , Huang Ruiping , Ireland James J. , Coussens Paul M. , Smith George W. 
Published: July 2004

Abstract
We recently obtained evidence that cocaine- and amphetamine-regulated transcript (CART), a potent anorectic neuropeptide, is expressed in the bovine ovary. The objectives of this study were to characterize bovine ovarian CART and determine its localization, regulation, and regulatory role during follicular development. CART mRNA was detected in stroma of adult ovaries and in large follicles, but was undetectable in several peripheral tissues, fetal ovaries, and corpora lutea. Within the ovary, CART mRNA and peptide were localized to the granulosal layer of some, but not all, antral follicles, with low, but detectable, expression in oocytes and cumulus cells. CART mRNA was undetectable in granulosal cells of dominant ovulatory follicles collected before and after the preovulatory gonadotropin surge, but was detected in the granulosal layer of adjacent subordinate follicles. In addition, amounts of CART mRNA and follicular fluid concentrations of CART peptide were greater in subordinate follicles vs. dominant follicles of the first follicular wave. Furthermore, CART treatment inhibited basal estradiol production, but not progesterone production, by granulosal cells in a dose-dependent fashion, and the effect was dependent on stage of cell differentiation. We conclude that granulosal cell CART expression is temporally regulated and potentially associated with follicle health status, and CART can inhibit granulosal cell estradiol production. Thus, CART may be a novel local regulator of follicular atresia in the bovine ovary.
Cocaine- and Amphetamine-Regulated Transcript Activates the Hypothalamic-Pituitary-Adrenal Axis through a Corticotropin-Releasing Factor Receptor-Dependent Mechanism
Authors: Smith Sean M. , Vaughan Joan M. , Donaldson Cynthia J. , Rivier Jean , Li Chien , Chen Alon , Vale Wylie W. 
Published: July 2004

Abstract
Cocaine- and amphetamine-regulated transcript (CART) is a highly expressed hypothalamic transcript that is concentrated in areas associated with the stress response. There is evidence for a role of CART in the regulation of the hypothalamic-pituitary-adrenal (HPA) axis. However, it is not clear whether CART regulates activity of the HPA axis by directly stimulating ACTH release from pituitary corticotropes or through interaction with hypothalamic factors. To address this issue, the effects of central and peripheral administration of CART on the HPA axis were compared. Central administration of CART(55–102) (1 μg) significantly increased circulating levels of ACTH (481 ± 122 vs. 93 ± 14 pg/ml; CART vs. vehicle) and corticosterone (460 ± 29 vs. 179 ± 62 ng/ml; CART vs. vehicle). In contrast, iv injection of CART(55–102) (0.09-9.0 nmol/kg) did not significantly affect circulating levels of ACTH or corticosterone. The corticotropin-releasing factor (CRF) receptor antagonist Astressin B was used to determine whether CART(55–102) elicits ACTH secretion via a CRF receptor-dependent mechanism. Injection of Astressin B (50 μg/kg, iv) inhibited CART(55–102)-induced ACTH and corticosterone responses. The effects of CART(55–102) on CRF and arginine vasopressin (AVP) expression were also examined in static hypothalamic explants. RT-PCR analysis revealed a significant up-regulation of CRF and AVP mRNA levels after CART(55–102) (10 nm and 1 μm) treatment. Last, the effects of CART(55–102) on CRF- and AVP-mediated ACTH release was investigated in dispersed rat anterior pituitary cells. Incubation of CART(55–102) (10–100 nm) did not significantly affect ACTH release from anterior pituitary cells. Findings from the present study suggest that CART regulates activity of the HPA axis through a CRF-dependent central mechanism and not by means of direct interaction with pituitary corticotropes.
Region-Specific Leptin Resistance within the Hypothalamus of Diet-Induced Obese Mice
Authors: Münzberg Heike , Flier Jeffrey S. , Bjørbæk Christian 
Published: July 2004

Abstract
Leptin resistance in diet-induced obese (DIO) mice is characterized by elevated serum leptin and a decreased response to exogenous leptin and is caused by unknown defects in the central nervous system. Leptin normally acts on several brain nuclei, but a detailed description of leptin resistance within individual brain regions has not been reported. We first mapped leptin-responsive cells in brains from DIO mice using phospho-signal transducer and activator of transcription (P-STAT3) immunohistochemistry. After 16 wk of high-fat-diet feeding, leptin-activated P-STAT3 staining within the arcuate nucleus (ARC) was dramatically decreased. In contrast, other hypothalamic and extrahypothalamic nuclei remained leptin sensitive. Reduced leptin-induced P-STAT3 in the ARC could also be detected after 4 wk and as early as 6 d of a high-fat diet. To examine potential mechanisms for leptin-resistant STAT3 activation in the ARC of DIO mice, we measured mRNA levels of candidate signaling molecules in the leptin receptor-STAT3 pathway. We found that the level of suppressor of cytokine signaling 3 (SOCS-3), an inhibitor of leptin signaling, is specifically increased in the ARC of DIO mice. The study suggests that the ARC is selectively leptin resistant in DIO mice and that this may be caused by elevated suppressor of cytokine signaling 3 in this hypothalamic nucleus. Defects in leptin action in the ARC may play a role in the pathogenesis of leptin-resistant obesity.
A Possible Mechanism for the Action of Adrenomedullin in Brain to Stimulate Stress Hormone Secretion
Authors: Taylor Meghan M. , Samson Willis K. 
Published: July 2004

Abstract
Adrenomedullin (AM) has been reported to have actions at each level of the hypothalamo-pituitary-adrenal (HPA) axis, suggesting that the peptide plays a role in the organization of the neuroendocrine responses to stress. We examined the mechanism by which AM regulates the central nervous system branch of the HPA axis as well as the possible role of AM in the modulation of the releases of two other hormones, prolactin and GH, whose secretions also are altered by stress. Intracerebroventricular administration of AM led to elevated plasma corticosterone levels in unrestrained, conscious male rats. This effect was abrogated by pretreatment with a CRH antagonist, suggesting that AM activates the HPA axis by causing the release of CRH into hypophyseal portal vessels. In addition, AM given intracerebroventricularly stimulated the release of prolactin but did not alter the secretion of GH. We propose that AM produced in the brain may be an important neuromodulator of the hormonal stress response.
Case Study: Comparison between the Acoustic Performance of a Mixed Building Technology Building and a Conventional Building
Authors: Bragança Luís , Patrício Jorge 
Published: July 2004

The objective of this work is to compare the acoustical performance of MBT (Mixed Building Technology) constructions and conventional buildings. The sound insulation performance of a MBT construction was assessed by tests done in situ. The results were compared with similar data from earlier measurements undertaken by the Building Physics Laboratory of the University of Minho in Portugal, and from simplified prediction methods. The building where this comparison was done is a 3-storey building. The first 2 storeys were refurbished using conventional construction methods, but the 3rd storey was built using MBT methods, characterised by using lightweight materials, with high thermal insulation, and large fenestration areas. Based on the work undertaken, some conclusions and proposals for further work are presented.
Potential Interaction Between Telithromycin and Warfarin
Authors: Kolilekas Likurgos , Anagnostopoulos George K , Lampaditis Ioannis , Eleftheriadis Iordanis 
Published: July 2004

OBJECTIVE: To report a case of warfarin—telithromycin interaction resulting in an elevated international normalized ratio (INR) and hemoptysis. CASE SUMMARY: A 73-year-old white man developed an elevated INR and mild hemoptysis as a result of an interaction between warfarin and telithromycin 800 mg/day. The INR increased from 3.1 before telithromycin was started to 11 after 5 days of telithromycin therapy. The INR returned to the therapeutic range 4 days after telithromycin was discontinued. DISCUSSION: Telithromycin is the first member of the macrolide subclass of ketolides and offers potential advantages over traditional macrolides/azalides for community-acquired respiratory tract infections caused by macrolide-resistant pathogens. As of July 16, 2004, bleeding complications and an increased INR as a result of an interaction between warfarin and telithromycin have not been described. Although the mechanism for this interaction remains unknown, it is suspected that it is a result of the inhibition of the metabolism of the R-isomer of warfarin, which is metabolized predominantly by CYP1A2 and less by CYP3A4. Further research is required to elucidate this issue. An objective causality assessment revealed that this adverse drug event as a result of the warfarin and telithromycin interaction was probable. CONCLUSIONS: We recommend close monitoring of INR levels in patients on warfarin who receive telithromycin therapy in an effort to control and prevent bleeding complications.
Multidrug-Resistant Acinetobacter Infections: An Emerging Challenge to Clinicians
Authors: Jain Rupali , Danziger Larry H 
Published: July 2004

OBJECTIVE: To review and evaluate clinically relevant epidemiology, microbiology, and clinical studies regarding the treatment of multidrug-resistant Acinetobacter infections. DATA SOURCES: Pertinent literature was identified by a MEDLINE search (1966-September 2003) and through secondary bibliographies of pertinent articles. STUDY SELECTION AND DATA EXTRACTION: All English-language articles identified from data sources were evaluated for clinical relevance. DATA SYNTHESIS: Acinetobacter baumannii has emerged as a worldwide problem as a nosocomial pathogen in hospitalized patients. Acinetobacter spp. can cause a multitude of infections including pneumonia, bacteremia, meningitis, urinary tract infections, and skin and soft tissue infections, and the mortality associated with these infections is high. Isolates resistant to almost all commercially available antimicrobials have been identified, thus limiting treatment options. The development of new agents and reappraisal of older compounds (ie, polymyxins, ampicillin/sulbactam) are necessary as we consider the optimal treatment of these multidrug-resistant organisms. CONCLUSIONS: There is no simple answer to the treatment of Acinetobacter infections. Eradication of Acinetobacter spp. requires adherence to good infection control practices and prudent antibiotic use, as well as effective antimicrobial therapy. Alternative therapies such as colistin, ampicillin/sulbactam, and tetracycline are potential options, but prospective, randomized, controlled trials are still lacking.
CD40 Ligand: A Novel Target in the Fight against Cardiovascular Disease
Authors: Vishnevetsky Diana , Kiyanista Vladimir A , Gandhi Pritesh J 
Published: July 2004

OBJECTIVE: To discuss the role of CD40 ligand (CD40L) in atherosclerosis and acute coronary syndromes (ACS), as well as describe relevant clinical literature evaluating the effects of pharmacotherapeutic agents on CD40L expression and soluble CD40L levels. DATA SOURCES: A MEDLINE and EMBASE search (1966–September 2003) was conducted using the key terms CD40, CD40 ligand, platelets, inflammation, and drug therapy. Additional primary literature was identified by reviewing the reference lists of relevant original and review papers. STUDY SELECTION AND DATA EXTRACTION: All articles identified in the search were evaluated, and those deemed relevant were incorporated into the review. DATA SYNTHESIS: CD40L is a transmembrane protein expressed on T cells, B cells, mast cells, basophils, eosinophils, natural killer cells, macrophages, endothelial cells, vascular smooth muscle cells, and activated platelets. It is also found in plasma as a soluble protein, sCD40L. As a consequence of CD40L binding to its receptor (CD40), several inflammatory processes are initiated. Studies have demonstrated elevated CD40L levels in patients with hypercholesterolemia and ACS, and elevated sCD40L levels have been associated with increased risk of cardiovascular events. Statins, glitazones, glycoprotein IIb/IIIa inhibitors, and clopidogrel have been demonstrated to effectively reduce CD40L levels both in vitro and in vivo. Abciximab has been shown to reduce the occurrence of death or myocardial infarction during 6 months of follow-up in patients with ACS who had the highest levels of sCD40L. CONCLUSIONS: The proinflammatory and procoagulant protein CD40L represents a novel target in the treatment of atherosclerosis and ACS. A number of therapeutic agents have been shown to modulate the expression of CD40L, findings that could have important clinical applications.