bluuebunny/crossref_metadata_2025 huggingface dataset:
Paratooite-(La), a new lanthanum-dominant rare-earth copper carbonate from Paratoo, South Australia
Authors: Pring A. , Wallwork K. , Brugger J. , U. Kolitsch
Published: March 2006

Paratooite-(La) is a new lanthanum-dominant rare-earth copper carbonate from the Paratoo copper mine, near Yunta, Olary district, South Australia. Paratooite-(La) occurs as sheaves and radiating sprays of blade-like to tabular pale blue crystals in thin fissures in a slaty country rock. Individual crystals are typically 50–200 μm in maximum dimension but <5 μm thick. Associated minerals include donnayite-(Y), kamphaugite-(Y), and bastnäsite-(La). Electron microprobe and CHN analyses gave: La2O3 26.47; Pr2O3 7.74; Nd2O3 8.15; Sm2O3 0.66; Gd2O3 0.85; Y2O3 0.72; CaO 7.57; SrO 3.15; Na2O 3.3; CuO 5.77; F 0.24; CO2 32.05; NO2 1.12; -O=F -0.10; sum 100.03, yielding an empirical formula of (La3.54Ca2.94Na2.32Nd1.05Pr1.03Sr0.66Y0.14Gd0.10Sm0.08)Σ11.86Cu1.58(C15.84N0.53)O47.76F0.24. The simplified formula is (REE ,Ca,Na,Sr)6Cu(CO3)8 or possibly REE3(Ca,Sr)2NaCu(CO3)8. The mineral is pale turquoise-blue to pale blue in colour, transparent, with a pearly to vitreous lustre and a pale blue streak. No cleavage was observed but the morphology and TEM studies indicate a cleavage parallel to ﹛100﹜. The Mohs hardness is estimated to be 4. The strongest lines in the X-ray powder pattern are [dobs (Iobs) (hkl )]: 5.047 (53) (200); 4.786 (49) (021); 3.957 (43) (220); 3.468 (43) (012, 221); 2.927 (100) (202); 2.530 (52) (241); 2.344 (22) (420,103); 2.232 (20) (421). A synchrotron powder diffraction pattern was indexed on a primitive orthorhombic cell with a = 10.0862(5), b = 12.8088(6), c = 7.2360(4) Å, V= 934.8(1) Å3 and Z = 2. The crystal structure of the new mineral could not be determined but powder diffraction data indicate the space group is probably P 222, Pmmm , P 2221 or Pmm2. The measured density is 3.68(3) g/cm3 and the calculated density is 3.78 g/cm3. Paratooite-(La) is biaxial negative with α = 1.605(3), β = 1.696(3) and γ = 1.752(2); pleochroism is medium strong; X very pale bluish, Y and Z bluish (with greenish tint) with absorption Z ≈ Y >> X. Paratooite-(La) is a supergene mineral which precipitated from mildly basic carbonated groundwaters. The mineral is named for the type locality.
The chemokine CXCL13 is a key molecule in autoimmune myasthenia gravis
Authors: Meraouna Amel , Cizeron-Clairac Geraldine , Panse Rozen Le , Bismuth Jacky , Truffault Frederique , Tallaksen Chantal , Berrih-Aknin Sonia
Published: March 2006

Myasthenia gravis (MG) is associated with ectopic germinal centers in the thymus. Thymectomy and glucocorticoids are the main treatments but they induce operative risks and side effects, respectively. The aim of this study was to propose new therapies more efficient for MG. We hypothesized that molecules dysregulated in MG thymus and normalized by glucocorticoids may play a key role in thymic pathogenesis. Using gene chip analysis, we identified 88 genes complying with these criteria, the most remarkable being the B-cell chemoattractant (CXCL13). Its expression was increased in thymus and sera of glucocorticoid-untreated patients and decreased in response to treatment in correlation with clinical improvement. Normal B cells were actively chemoattracted by thymic extracts from glucocorticoid-untreated patients, an effect inhibited by anti-CXCL13 antibodies. In the thymus, CXCL13 was preferentially produced by epithelial cells and overproduced by epithelial cells from MG patients. Altogether, our results suggest that a high CXCL13 production by epithelial cells could be responsible for germinal center formation in MG thymus. Furthermore, they show that this gene is a main target of corticotherapy. Thus, new therapies targeting CXCL13 could be of interest for MG and other autoimmune diseases characterized by ectopic germinal center formation.
Circulating endothelial-cell kinetics and viability predict survival in breast cancer patients receiving metronomic chemotherapy
Authors: Mancuso Patrizia , Colleoni Marco , Calleri Angelica , Orlando Laura , Maisonneuve Patrick , Pruneri Giancarlo , Agliano Alice , Goldhirsch Aron , Shaked Yuval , Kerbel Robert S. , Bertolini Francesco
Published: March 2006

Antiangiogenic agents and therapeutic strategies have entered the clinical oncology arena. The classical tumor size measurements defined to monitor efficacy of chemotherapy, however, might not be appropriate for these newer therapeutics. We previously found that circulating endothelial cells (CECs) were increased in number and more viable in cancer patients compared with control subjects. We investigated the correlation between CEC kinetics and clinical outcome in patients with advanced breast cancer receiving metronomic chemotherapy, a therapeutic strategy associated with antiangiogenic activity and anticancer efficacy. CEC number and viability were measured by flow cytometry in patients and in preclinical models. CECs were decreased in patients for whom no overall clinical benefit (defined as a clinical response or a stable disease) was observed compared with those who had a clinical benefit (P = .015). This difference was due to an increased fraction of apoptotic CECs in patients with a clinical benefit. Univariate and multivariate analyses indicated that CEC values greater than 11/μL were associated with a longer progression-free survival (P = .001) and an improved overall survival (P = .005). Preclinical models indicated that the source of apoptotic CECs was most likely the tumor vasculature. CEC kinetics and viability are very promising as predictors of clinical response in patients undergoing metronomic chemotherapy.
Vehicle exhaust exposure in an incident case–control study of adult asthma
Authors: Modig L. , Järvholm B. , Rönnmark E. , Nyström L. , Lundbäck B. , Andersson C. , Forsberg B.
Published: March 2006

The objective of this case–control study was to evaluate whether traffic-related air pollution exposure at home increases the risk of asthma in adults and to compare two commonly used exposure variables and differences between urban and rural living.

Incident cases of asthma and matched controls of subjects aged 20–60 yrs were recruited in Luleå, Sweden. In total 203 cases and 203 controls were enrolled in the study. Exposure was estimated by traffic flow and measured levels of outdoor nitrogen dioxide (NO2) in the surrounding environment of each home, respectively. The relationship between measured levels of NO2and traffic flow was studied using linear regression.

The results indicated a nonsignificant tendency between living in a home close to a high traffic flow and an increased risk of asthma. The association between asthma and measured NO2was weak and not significant, but the skin-prick test result acted as an effect modifier with a borderline significant association among positives. The correlation between traffic flow and outdoor NO2was low.

The results suggest that living close to high traffic flows might increase the asthma incidence in adults, while the tendency for nitrogen dioxide was only seen among atopics. Traffic flow and nitrogen dioxide had a lower than expected correlation.
Use of a T-cell-based test for detection of tuberculosis infection among immunocompromised patients: Table 1—
Authors: Piana F. , Codecasa L. R. , Cavallerio P. , Ferrarese M. , Migliori G. B. , Barbarano L. , Morra E. , Cirillo D. M.
Published: March 2006

The aim of this study was to compare the performance of the T-SPOT.TBTMtest, a T-cell-based test, with the tuberculin skin test (TST) in the diagnosis of latent tuberculosis (TB) infection.

The study was carried out in 138 immunosuppressed haematology patients who had been nosocomially exposed to a case of smear-positive TB.

Overall, 44.2% of the contacts were positive by T-SPOT.TBTMtest, and 17.4% by TST (concordance 67.8%). The apparent prevalence of infection fell from 25.9 to 14.5% with the TST with increasing immunosuppression, although this difference was not significant. In contrast, the apparent prevalence of infection with the T-SPOT.TBTMtest was unaffected at 44.6 and 44.3%, respectively. The T-SPOT.TBTMtest had an overall indeterminate rate of 4.3%, and this was also unaffected by the level of immunosuppression.

This study suggests that the T-SPOT.TBTMtest maintains its sensitivity and performance in immunocompromised patients, identifying a large number of truly infected patients anergic to the tuberculin skin test.
Cardiopulmonary stress during exercise training in patients with COPD
Authors: Probst V. S. , Troosters T. , Pitta F. , Decramer M. , Gosselink R.
Published: March 2006

Exercise training is an essential component of pulmonary rehabilitation. However, the cardiopulmonary stress imposed during different modalities of exercise training is not yet known.

In the present study, the cardiopulmonary stress of a 12-week exercise training programme in 11 chronic obstructive pulmonary disease (COPD) patients (forced expiratory volume in one second 42±12%pred, age 69±6 yrs) was measured. Pulmonary gas exchange and cardiac frequency (fC) of three training sessions were measured with a portable metabolic system at the beginning, mid-term and end of the programme. Symptoms were assessed with Borg scores.

The exercise intensity was compared with the recommendations for exercise training by the American College of Sports Medicine (ACSM). Training effects were significant (maximum change in work: 14±11 Watts, 6-min walk test: 44±36 m). Whole body exercises (cycling, walking and stair climbing) consistently resulted in higher cardiopulmonary stress (oxygen uptake (V′O2), minute ventilation andfC) than arm cranking and resistance training. Dyspnoea was higher during cycling than resistance training. Patients exercised for >70% (>20 min) of the total exercise time at >40% of theV′O2reserve andfCreserve (“moderate” intensity according to the ACSM) throughout the programme.

The cardiopulmonary stress resistance training is lower than during whole-body exercise and results in fewer symptoms. In addition, exercise testing based on guidelines using a fixed percentage of baseline peak performance and symptom scores achieves and sustains training intensities recommended according to the American College of Sports Medicine.
Does expiratory flow limitation predict chronic dyspnoea in adults with cystic fibrosis?
Authors: Holland A. E. , Denehy L. , Wilson J. W.
Published: March 2006

Tidal expiratory flow limitation (EFL) may promote dynamic hyperinflation and contribute to chronic dyspnoea. The purpose of this study was to assess the contribution of EFL to chronic dyspnoea in adults with cystic fibrosis (CF).

The presence of EFL was determined in 102 adults with stable CF (forced expiratory volume in one second (FEV1) 17.3–91.5% predicted) and 20 age-matched control subjects using the negative expiratory pressure technique. Measurements of inspiratory capacity (IC) and spirometry were performed, and chronic dyspnoea was evaluated using the modified Medical Research Council scale.

EFL was present in 34 subjects (33%), with 18 subjects flow limited in the sitting position and 16 subjects flow limited only in the supine position. Flow limitation in the sitting position was associated with older age and lower FEV1compared with flow-limited supine position and non-flow-limited subjects. A significant reduction in IC accompanied EFL in both the sitting and supine positions. Flow limitation in the sitting position was associated with significantly higher levels of chronic dyspnoea. Ordinal regression analysis indicated that EFL was the best predictor of chronic dyspnoea in a model that included FEV1% pred.

Expiratory flow limitation in cystic fibrosis is associated with reduced forced expiratory volume in one second, older age and dynamic hyperinflation. Expiratory flow limitation significantly contributes to chronic dyspnoea in cystic fibrosis.
Short-term effects of nitrogen dioxide on mortality: an analysis within the APHEA project
Authors: Samoli E. , Aga E. , Touloumi G. , Nisiotis K. , Forsberg B. , Lefranc A. , Pekkanen J. , Wojtyniak B. , Schindler C. , Niciu E. , Brunstein R. , Dodič Fikfak M. , Schwartz J. , Katsouyanni K.
Published: March 2006

The short-term effects of nitrogen dioxide (NO2) on total, cardiovascular and respiratory mortality in 30 European cities participating in the Air Pollution on Health: a European Approach (APHEA)-2 project were investigated.

The association was examined using hierarchical models implemented in two stages. In the first stage, data from each city were analysed separately, whereas in the second stage, the city-specific air pollution estimates were regressed on city-specific covariates to obtain overall estimates and to explore sources of possible heterogeneity.

A significant association of NO2with total, cardiovascular and respiratory mortality was found, with stronger effects on cause-specific mortality. There was evidence of confounding in respiratory mortality with black smoke and sulphur dioxide. The effect of NO2on total and cardiovascular mortality was observed mainly in western and southern European cities, and was larger when smoking prevalence was lower and household gas consumption was higher. The effect of NO2on respiratory mortality was higher in cities with a larger proportion of elderly persons in the population and higher levels of particulate matter with a 50% cut-off aerodynamic diameter of 10 μm.

The results of this large study are consistent with an independent effect of nitrogen dioxide on mortality, but the role of nitrogen dioxide as a surrogate of other unmeasured pollutants cannot be completely ruled out.
A small amount of inhaled nitric oxide does not increase lung diffusing capacity
Authors: Zavorsky G. S. , Murias J. M.
Published: March 2006

The aim of the present study was to determine: 1) whether 40–50 ppm nitric oxide (NO) increases diffusing capacity of the lung for NO (DL,NO) and carbon monoxide (DL,CO), membrane diffusing capacity for CO (Dm,CO) and pulmonary capillary blood volume (Vc); 2) the actual number of tests required to provide a reasonable estimate ofDL,NO,DL,CO,Dm,COandVc; and 3) repeatability of these parameters using the single-breathDL,NO–DL,COmethod.

In total, 31 subjects performed five single-breath hold manoeuvres at rest, inhaling 43±3 ppm NO together with a standard diffusion mixture.

DL,NO(Dm,CO) remained unchanged from the first to fifth trial. However, compared with the first trial,DL,COandVchad decreased by the fourth (−4±5%; 95% confidence interval (CI) = −5– −2%) and third trial (−5±7%; 95% CI = −7– −2%), respectively. Repeatability over five trials was 17, 3 and 7 mL·min−1·mmHg−1forDL,NO,DL,COandDm,CO, respectively, and 13 mL forVcwhenDm,CO = DL,NO/2.42.

In conclusion, nitric oxide inhaled during sequential single-breath manoeuvres has no effect on diffusing capacity of the lung for nitric oxide and, thus, membrane diffusing capacity for carbon monoxide. Since more than two and three trials will lower pulmonary capillary blood volume and diffusing capacity of the lung for carbon monoxide, respectively, the average value of only two properly performed trials is suggested.
Hysteresis effects studied by numerical simulations: Cyclic loading-unloading of a realistic sand model
Authors: García Xavier , Medina Ernesto A.
Published: March 2006

When Hertz-Mindlin force laws are considered in the context of the effective-medium theory, the predictions yield a constant Poisson coefficient and bulk/shear elastic moduli that scale with pressure with a 1/3 power law exponent [Formula: see text]. This prediction contradicts early and recent experimental findings that conclude moduli grow faster with a 1/2 power law exponent ([Formula: see text]). Such a conclusion is also reached by recent second-order corrections to linear elastic theory. In this work we use a discrete-particle method to study the elastic response of a model of sand that is unconsolidated because of cyclic loading. We use a detailed molecular dynamics simulation that accounts for Hertz-type grain interactions and history-dependent shear forces. The porous sand model is constructed from spherical particles whose size distribution mimics well-sorted unconsolidated sands. The geometry of the model is obtained by simulating critical processes in sedimentary rock formations. Hysteretic behavior and relations between the sample bulk modulus, strain, and stress are obtained. The simulated sample reproduces experimental transient and stationary loading-unloading behavior. We find good correspondence of pressure and strain dependence of elastic moduli in our model with semilinear elasticity theory predictions. Simple arguments explain low coordination numbers observed on force-transmitting samples and the tendency to reduce dissipation under cyclic loading. Our approach clearly shows that a Hertz-Mindlin grain interaction is not inconsistent with the experimental [Formula: see text] behavior of the bulk modulus.
Application of piezoelectric and seismoelectrokinetic phenomena in exploration geophysics: Review of Russian and Israeli experiences
Authors: Neishtadt Nahum M. , Eppelbaum Lev V. , Levitski Alex G.
Published: March 2006

Systematic research of piezoelectric and seismoelectrokinetic phenomena in the context of exploration geophysics began in the former Soviet Union in the mid-1950s. These phenomena are manifested by electrical and electromagnetic (EM) processes that occur in rocks under the influence of elastic oscillations triggered by shots or mechanical impacts (hits). This paper presents a classification of piezoelectric and seismoelectrokinetic phenomena, which is based on the analysis of abundant theoretical, laboratory, and field data accumulated mainly by Soviet, Russian, and Israeli researchers. This classification divides the above phenomena into the following types: (1) the seismoelectrokinetic (electrokinetic) phenomenon E, which occurs in poly-phase media because of the mutual displacement of the solid and liquid phases; (2) the piezoelectric phenomenon, which occurs in rocks that contain piezoactive minerals; (3) the shot-triggered phenomenon, observed in rocks in the vicinity of a shotpoint or hit point; (4) the seismoelectric phenomenon I, manifested by the change of the electric current passing through rock; and (5) high-frequency impulse EM radiation, generated by massive base-metal bodies. This paper describes these five phenomena in detail — their nature, manifestation patterns, and registration techniques. Because the manifestation patterns of the phenomena differ in various types of rock, the phenomena can be used as a basis for geophysical exploration techniques. The piezoelectric method is an example of a successful application of piezoelectric and seismoelectrokinetic phenomena in exploration geophysics. This method was developed in the former Soviet Union, and it has been applied successfully in mineral exploration and research in Russia and, recently, in the West. The method uses a new geophysical parameter: piezoelectric activity of rocks, ores, and minerals. It enables direct exploration for pegmatite, apatite-nepheline, sphalerite, and ore-quartz deposits of gold, tin, tungsten, molybdenum, zinc, crystal, and other raw materials. This method also differentiates rocks such as bauxites and kimberlites from host rocks by their electrokinetic properties.
Traveltime approximations for a layered transversely isotropic medium
Authors: Ursin Bjørn , Stovas Alexey
Published: March 2006

We consider multiple transmitted, reflected, and converted qP-qSV-waves or multiple transmitted and reflected SH-waves in a horizontally layered medium that is transversely isotropic with a vertical symmetry axis (VTI). Traveltime and offset (horizontal distance) between a source and receiver, not necessarily in the same layer, are expressed as functions of horizontal slowness. These functions are given in terms of a Taylor series in slowness in exactly the same form as for a layered isotropic medium. The coefficients depend on the parameters of the anisotropic layers through which the wave has passed, and there is no weak anisotropy assumption. Using classical formulas, the traveltime or traveltime squared can then be expressed as a Taylor series in even powers of offset. These Taylor series give rise to a shifted hyperbola traveltime approximation and a new continued-fraction approximation, described by four parameters that match the Taylor series up to the sixth power in offset. Further approximations give several simplified continued-fraction approximations, all of which depend on three parameters: zero-offset traveltime, NMO velocity, and a heterogeneity coefficient. The approximations break down when there is a cusp in the group velocity for the qSV-wave. Numerical studies indicate that approximations of traveltime squared are generally better than those for traveltime. A new continued-fraction approximation that depends on three parameters is more accurate than the commonly used continued-fraction approximation and the shifted hyperbola.
HFVS™: Enhanced data quality through technology integration
Authors: Krohn Christine E. , Johnson Marvin L.
Published: March 2006

Known problems with vibroseis data include difficult-to-pick and inaccurate first-arrival times, poor well ties, correlation side lobes, harmonic ghosts, and coupling differences. Also, to reduce acquisition costs, various methods are used to record and then separate data from different source locations using vibrators sweeping simultaneously, but these methods suffer from poor data separation and harmonic contamination. A novel combination of heritage Mobil High Fidelity Vibratory Seismic (HFVS) and heritage Exxon vibrator technologies solves these problems with vibroseis data. The method involves vibrator separation combined with vibrator signature deconvolution in such a manner that the output is minimum phase and matches impulsive data. Vibrator signatures are calculated from the vibrator accelerometer measurements. The signatures from multiple vibrators and multiple sweeps are used to design a filter that optimally separates the data from each vibrator and replaces the signatures with a specially designed impulse response. Specific procedures are included to reduce the effects of inversion noise, which can distort the phase. HFVS recording can be used to increase production rates and reduce acquisition costs or to increase spatial sampling and improve data quality. Data recorded from multiple vibrators sweeping simultaneously can be separated by at least 60 dB. After separation, the data from each vibrator can be processed as unique source points. Compared with traditional vibrator arrays, individually processing each source point can result in better data quality by reducing intra-array effects and improving the mitigation of ground-roll noise.
Identification of calibration errors in helicopter electromagnetic (HEM) data through transform to the altitude-corrected phase-amplitude domain
Authors: Ley-Cooper Yusen , Macnae James , Robb Terry , Vrbancich Julian
Published: March 2006

We investigate the properties of EM signals in several different response-parameter domains to identify calibration errors in helicopter electromagnetic (HEM) data. In particular, we define a dimensionless response parameter α, derived from frequency-domain data, that is numerically identical to the historic wire-loop response parameter, and is closely related to the thin-sheet and half-space response parameters. The arctangent of α is the phase ϕ of the secondary field. We further define a dimensionless amplitude response parameter β, calculated as the ratio between inductive limits estimated from the data and from system geometry. The inductive limit calculated from geometry provides an initial altitude correction to the data amplitudes. Additional data corrections further correct phase effects and altimeter variations. The amplitude and phase errors in calibration become independent differences between the data and the fitted model in the ϕβ domain. This investigation was undertaken in the response-parameter domain rather than in the data domain, allowing the analysis to be independent of absolute values of conductivity and system frequencies. Statistical analysis in the ϕβ domain of recently acquired data suggests that amplitude calibration errors in HEM data may cause fitted models to have systematic depth errors of 1 to 2 m for near-surface conductors; variable altitude measurement errors are about 1.5 m over seawater.
Mapping thin resistors and hydrocarbons with marine EM methods: Insights from 1D modeling
Authors: Constable Steven , Weiss Chester J.
Published: March 2006

The use of marine controlled-source electromagnetic EM (CSEM) sounding to detect thin resistive layers at depths below the seafloor has been exploited recently to assess the resistivity of potential hydrocarbon reservoirs before drilling. We examine the sensitivity of the CSEM method to such layers with forward and inverse modeling in one and three dimensions. The 3D modeling demonstrates that if both source and receivers are over a tabular 3D target, 1D modeling predicts the observed response to very high accuracy. Experimental design can thus be based on 1D analysis in which hundreds of range and frequency combinations can be computed to find the optimal survey parameters for a given target structure. Modeling in three dimensions shows that the vertical electric-field response is largest over the edges of a 3D target. The 3D modeling also suggests that a target body needs to have a diameter twice the burial depth to be reliably seen by CSEM sounding. A simple air-wave model (energy propagating from source to receiver via the atmosphere) allows the effects of the target layer and atmosphere to be separated and shows where sensitivity to the target is diminished or lost because of finite water depth as a function of range, frequency, and seafloor resistivity. Unlike DC resistivity sounding, the marine CSEM method is not completely T-equivalent and, in principle, can resolve resistivity and thickness separately. Smooth inversion provides an estimate of the method's resolving power and highlights the fact that although the radial CSEM fields contain most of the sensitivity to the thin resistive target, inverted alone they produce only increasing resistivity with depth. Inclusion of the radial mode CSEM data forces the recovery of the thin resistor, but magnetotelluric data can be used more effectively to achieve the same result.
Airborne electromagnetic footprints in 1D earths
Authors: Reid James E. , Pfaffling Andreas , Vrbancich Julian
Published: March 2006

Existing estimates of footprint size for airborne electromagnetic (AEM) systems have been based largely on the inductive limit of the response. We present calculations of frequency-domain, AEM-footprint sizes in infinite-horizontal, thin-sheet, and half-space models for the case of finite frequency and conductivity. In a half-space the original definition of the footprint is extended to be the side length of the cube with its top centered below the transmitter that contains the induced currents responsible for 90% of the secondary field measured at the receiver. For a horizontal, coplanar helicopter frequency-domain system, the in-phase footprint for induction numbers less than 0.4 (thin sheet) or less than 0.6 (half-space) increases from around 3.7 times the flight height at the inductive limit to more than 10 times the flight height. For a vertical-coaxial system the half-space footprint exceeds nine times the flight height for induction numbers less than 0.09. For all models, geometries, and frequencies, the quadrature footprint is approximately half to two-thirds that of the in-phase footprint. These footprint estimates are supported by 3D model calculations that suggest resistive targets must be separated by the footprint dimension for their individual anomalies to be resolved completely. Analysis of frequency-domain AEM field data acquired for antarctic sea-ice thickness measurements supports the existence of a smaller footprint for the quadrature component in comparison with the in-phase, but the effect is relatively weak. In-phase and quadrature footprints estimated by comparing AEM to drillhole data are considerably smaller than footprints from 1D and 3D calculations. However, we consider the footprints estimated directly from field data unreliable since they are based on a drillhole data set that did not adequately define the true, 3D, sea-ice thickness distribution around the AEM flight line.
Model-based separation filtering of magnetic data
Authors: Pilkington Mark , Cowan Duncan R.
Published: March 2006

Separating the fields produced by sources at different depths is a common requirement in the interpretation of potential field data. Approaches to this problem are generally data- or model-based. Data-based methods require clear linear segments in the logarithmic power spectrum of the data corresponding to different components of the field. Various types of filters can then be designed to carry out the separation. When the logarithmic power spectrum shows no identifiable linear spectral segments, other approaches are necessary. We outline a model-based method that does not depend on power-spectral information but requires independent estimates of the average depths of the source distributions, e.g., from seismic interpretations. An ensemble of models using fractal source distributions is computed based on these known values, and filter parameters are determined that produce the closest fit (in a least-squares sense) to the theoretical fields that each source distribution generates. This approach is used to separate basement effects from intrasedimentary sources in magnetic data collected over the Colville Hills, Northwest Territories, Canada. Seismic data interpretation places crystalline basement at ∼10 km depth and an intrasedimentary basaltic layer at ∼2 km. Our approach results in an optimal separation filter with a cutoff wavelength of ∼12 km that appears to provide an effective separation of the two source effects.
Target-oriented beamlet migration based on Gabor-Daubechies frame decomposition
Authors: Chen Ling , Wu Ru-Shan , Chen Yong
Published: March 2006

We develop beamlet propagation and imaging using Gabor-Daubechies (G-D) frame decomposition based on local perturbation theory and apply it to target-oriented prestack depth migration. The method is formulated with local background velocities and local perturbations in wavefield extrapolation. The localized propagators and phase-correction operators are obtained analytically or semianalytically by one-way operator decomposition and screen approximation in the beamlet and space-beamlet mixed domain. Beamlet wavefields have superior localization properties in both local space and direction (wave-number) over Gaussian beams in the sense that localizations are not limited within short propagation distances in either homogeneous or heterogeneous media. Comparisons of the prestack depth-migrated images for the 2D SEG-EAGE salt model and the Marmousi model indicate that, for seismic-wave propagation and imaging in complex structural environments, the G-D beamlet propagator has higher accuracy and better wide-angle properties than do global propagators. Target-oriented prestack G-D beamlet migration is performed by means of local-angle-domain imaging and controlled superposition of common-dip-angle images based on the local directivity features of the target structures. This considers the spatial and direction localizations of beamlets. As a numerical example, we process the 2D SEG-EAGE salt-model prestack data. The results show that the proposed migration method has considerable advantages in suppressing noise and enhancing structural features. Image quality for subsalt structures, especially for steep faults, is improved through structure-based superposition of common-angle images. This demonstrates the potential and capability of beamlet migration in target-oriented seismic imaging.
Viscoelasticity of precompacted unconsolidated sand with viscous cement
Authors: Leurer Klaus C. , Dvorkin Jack
Published: March 2006

The elastic properties of sand strongly depend on the grains’ contact stiffness, which can be increased significantly by solid matter and, depending on frequency, viscous fluid acting as contact cement. To calculate seismic velocities in precompacted fluid-cemented sand, we examine how a small amount of viscous fluid at the grain contacts influences their normal and tangential stiffnesses as a function of effective pressure. Using the Hertz-Mindlin approach and considering oscillatory loading in addition to precompaction of a combination of two elastic spheres, we extend the dry-contact elastic theory by a viscoelastic formulation. Here, we describe the radial flow of the fluid cement induced by the oscillations of the grains’ surfaces around the direct contact, a process that leads to a complex normal stiffness and stiffness/frequency dispersion. In the resulting combined model, the low-frequency real part of the complex normal stiffness identical is to the original Hertz-Mindlin expression. The magnitude of the dispersion is governed by the amount of viscous cement; magnitude decreases as effective pressure increases. The frequency of the maximum imaginary part of the normal stiffness is determined mainly by cement viscosity and contact geometry. The tangential contact stiffness virtually is not influenced by the viscous fluid. Comparison of predicted results with data from pulse transmission experiments (500 kHz) on glass beads with two different fluids shows an excellent fit in P-wave velocities [Formula: see text], whereas S-wave velocities [Formula: see text] are systematically overestimated by the model. The experimental results confirm, however, the predicted change with effective pressure in the [Formula: see text] ratio for both examined cases as well as reflect the predicted increase in [Formula: see text] and [Formula: see text], respectively, between the two cases. This implies that our viscoelastic formulation represents a reasonable way to describe the role of viscous cement in sand.
A technique for identifying microseismic multiplets and application to the Valhall field, North Sea
Authors: Arrowsmith Stephen J. , Eisner Leo
Published: March 2006

A fast, fully automatic technique to identify microseismic multiplets in borehole seismic data is developed. The technique may be applied in real time to either continuous data or detected-event data for a number of three-component receivers and does not require prior information such as P- or S-wave time picks. Peak crosscorrelation coefficients, evaluated in the frequency domain, are used as the basis for identifying microseismic doublets. The peak crosscorrelation coefficient at each receiver is evaluated with a weighted arithmetic average of the normalized correlation coefficients of each component. Each component is weighted by the maximum amplitude of the signal for that component to reduce the effect of noise on the calculations. The weighted average correlations are averaged over all receivers in a time window centered on a fixed lag time. The size of the time window is determined from the dominant period in the signal, and the lag time is the time that maximizes the average correlation coefficient. The technique is applied to a three-component passive seismic data set recorded at the Valhall field, North Sea. A large number of microseismic doublets are identified that can be grouped into multiplets, reducing the total number of absolute event locations by a factor of two. Seven large multiplets reflect the repeated multiple rerupturing (up to 30 times on a single fault) and significant stress release. Two major faults dominate the seismic activity, causing at least one-fourth of the observed events.
Predictive removal of scattered noise
Authors: Herman Gérard C. , Perkins Colin
Published: March 2006

Land seismic data can be severely contaminated with coherent noise. We discuss a deterministic technique to predict and remove scattered coherent noise from land seismic data based on a mathematical model of near-surface wave propagation. We test the method on a unique data set recorded by Petroleum Development of Oman in the Qarn Alam area (with shots and receivers on the same grid), and we conclude that it effectively reduces scattered noise without smearing reflection energy.
Erythropoietin and neuroprotection: a therapeutic perspective
Authors: Milano M. , Collomp R.
Published: March 2006

Recombinant erythropoietin (EPO) is used to correct for anaemia caused by chronic renal failure or cancer therapy. Improvement of the quality of life of anaemic patients treated with EPO was recently demonstrated and preliminary clinical results suggest an improvement of cognitive functions in patients receiving EPO. High expression of EPO and its receptor in the brain during embryonic development has led to the investigation of not only the neurotrophic role of EPO but also its neuroprotective properties. The neuroprotective effects of EPO have various complementary actions including antagonism of the effects of glutamate, increased expression of antioxidant enzymes, changes in production of neurotransmitters and induction of neuroglobin. Convincing experimental results suggest a blood-brain transport of EPO whereas clinical pharmacokinetic data do not as yet support this. The neuroprotective effects of EPO and its therapeutic promise need to be underlined.
Suppressor of Cytokine Signaling-3 Inhibits Interleukin-1 Signaling by Targeting the TRAF-6/TAK1 Complex
Authors: Frobøse Helle , Groth Rønn Sif , Heding Peter E. , Mendoza Heidi , Cohen Philip , Mandrup-Poulsen Thomas , Billestrup Nils
Published: March 2006

IL-1 plays a major role in inflammation and autoimmunity through activation of nuclear factor κ B (NFκB) and MAPKs. Although a great deal is known about the mechanism of activation of NFκB and MAPKs by IL-1, much less is known about the down-regulation of this pathway. Suppressor of cytokine signaling (SOCS)-3 was shown to inhibit IL-1-induced transcription and activation of NFκB and the MAPKs JNK and p38, but the mechanism is unknown. We show here that SOCS-3 inhibits NFκB-dependent transcription induced by overexpression of the upstream IL-1 signaling molecules MyD88, IL-1R-activated kinase 1, TNF receptor-associated factor (TRAF)6, and TGFβ-activated kinase (TAK)1, but not when the MAP3K MAPK/ERK kinase kinase-1 is used instead of TAK1, indicating that the target for SOCS-3 is the TRAF6/TAK1 signaling complex. By coimmunoprecipitation, it was shown that SOCS-3 inhibited the association between TRAF6 and TAK1 and that SOCS-3 coimmunoprecipitated with TAK1 and TRAF6. Furthermore, SOCS-3 inhibited the IL-1-induced catalytic activity of TAK1. Because ubiquitination of TRAF6 is required for activation of TAK1, we analyzed the role of SOCS-3 on TRAF6 ubiquitination and found that SOCS-3 inhibited ubiquitin modification of TRAF6. These results indicate that SOCS-3 inhibits IL-1 signal transduction by inhibiting ubiquitination of TRAF6, thus preventing association and activation of TAK1.
Multiple epigenetic maintenance factors implicated by the loss of Mll2 in mouse development
Authors: Glaser Stefan , Schaft Julia , Lubitz Sandra , Vintersten Kristina , van der Hoeven Frank , Tufteland Katharina R. , Aasland Rein , Anastassiadis Konstantinos , Ang Siew-Lan , Stewart A. Francis
Published: March 2006

Epigenesis is the process whereby the daughters of a dividing cell retain a chromatin state determined before cell division. The best-studied cases involve the inheritance of heterochromatic chromosomal domains, and little is known about specific gene regulation by epigenetic mechanisms. Recent evidence shows that epigenesis pivots on methylation of nucleosomes at histone 3 lysines 4, 9 or 27. Bioinformatics indicates that mammals have several enzymes for each of these methylations, including at least six histone 3 lysine 4 methyltransferases. To look for evidence of gene-specific epigenetic regulation in mammalian development, we examined one of these six, Mll2, using a multipurpose allele in the mouse to ascertain the loss-of-function phenotype. Loss of Mll2 slowed growth, increased apoptosis and retarded development, leading to embryonic failure before E11.5. Using chimera experiments, we demonstrated that Mll2 is cell-autonomously required. Evidence for gene-specific regulation was also observed. Although Mox1 and Hoxb1 expression patterns were correctly established, they were not maintained in the absence of Mll2, whereas Wnt1 and Otx2were. The Mll2 loss-of-function phenotype is different from that of its sister gene Mll, and they regulate different Hox complex genes during ES cell differentiation. Therefore, these two closely related epigenetic factors play different roles in development and maintain distinct gene expression patterns. This suggests that other epigenetic factors also regulate particular patterns and that development entails networks of epigenetic specificities.
Autophagy occurs upstream or parallel to the apoptosome during histolytic cell death
Authors: Akdemir Fatih , Farkaš Robert , Chen Po , Juhasz Gabor , Medved'ová Lucia , Sass Miklos , Wang Lai , Wang Xiaodong , Chittaranjan Suganthi , Gorski Sharon M. , Rodriguez Antony , Abrams John M.
Published: March 2006

Histolysis refers to a widespread disintegration of tissues that is morphologically distinct from apoptosis and often associated with the stimulation of autophagy. Here, we establish that a component of the apoptosome, and pivotal regulator of apoptosis, is also required for histolytic cell death. Using in vivo and ex vivo assays, we demonstrate a global apoptogenic requirement for dark, the fly ortholog of Apaf1,and show that a required focus of dark- organismal lethality maps to the central nervous system. We further demonstrate that the Dark protein itself is a caspase substrate and find that alterations of this cleavage site produced the first hypermorphic point mutation within the Apaf1/Ced-4 gene family. In a model of `autophagic cell death', darkwas essential for histolysis but dispensable for characteristic features of the autophagic program, indicating that the induction of autophagy occurs upstream or parallel to histolytic cell death. These results demonstrate that stimulation of autophagy per se is not a `killing event' and, at the same time, establish that common effector pathways, regulated by the apoptosome,can underlie morphologically distinct forms of programmed cell death.
smoothenedandthickveinsregulate Moleskin/Importin 7-mediated MAP kinase signaling in the developingDrosophilaeye
Authors: Vrailas Alysia D. , Marenda Daniel R. , Cook Summer E. , Powers Maureen A. , Lorenzen James A. , Perkins Lizabeth A. , Moses Kevin
Published: March 2006

The Drosophila Mitogen Activated Protein Kinase (MAPK) Rolled is a key regulator of developmental signaling, relaying information from the cytoplasm into the nucleus. Cytoplasmic MEK phosphorylates MAPK (pMAPK), which then dimerizes and translocates to the nucleus where it regulates transcription factors. In cell culture, MAPK nuclear translocation directly follows phosphorylation, but in developing tissues pMAPK can be held in the cytoplasm for extended periods (hours). Here, we show that Moleskin antigen(Drosophila Importin 7/Msk), a MAPK transport factor, is sequestered apically at a time when lateral inhibition is required for patterning in the developing eye. We suggest that this apical restriction of Msk limits MAPK nuclear translocation and blocks Ras pathway nuclear signaling. Ectopic expression of Msk overcomes this block and disrupts patterning. Additionally,the MAPK cytoplasmic hold is genetically dependent on the presence of Decapentaplegic (Dpp) and Hedgehog receptors.
Chemoreceptor plasticity and respiratory acclimation in the zebrafishDanio rerio
Authors: Vulesevic B. , McNeill B. , Perry S. F.
Published: March 2006

The goals of this study were to assess the respiratory consequences of exposing adult zebrafish Danio rerio to chronic changes in water gas composition (hypoxia, hyperoxia or hypercapnia) and to determine if any ensuing effects could be related to morphological changes in branchial chemoreceptors. To accomplish these goals, we first modified and validated an established non-invasive technique for continuous monitoring of breathing frequency and relative breathing amplitude in adult fish. Under normal conditions 20% of zebrafish exhibited an episodic breathing pattern that was composed of breathing and non-breathing (pausing/apneic) periods. The pausing frequency was reduced by acute hypoxia (PwO2<130 mmHg)and increased by acute hyperoxia (PwO2>300 mmHg), but was unaltered by acute hypercapnia.

Fish were exposed for 28 days to hyperoxia (PwO2>350 mmHg), or hypoxia (PwO2=30 mmHg) or hypercapnia(PwCO2=9 mmHg). Their responses to acute hypoxia or hypercapnia were then compared to the response of control fish kept for 28 days in normoxic and normocapnic water. In control fish, the ventilatory response to acute hypoxia consisted of an increase in breathing frequency while the response to acute hypercapnia was an increase in relative breathing amplitude. The stimulus promoting the hyperventilation during hypercapnia was increased PwCO2 rather than decreased pH. Exposure to prolonged hyperoxia decreased the capacity of fish to increase breathing frequency during hypoxia and prevented the usual increase in breathing amplitude during acute hypercapnia. In fish previously exposed to hyperoxia,episodic breathing continued during acute hypoxia until PwO2 had fallen below 70 mmHg. In fish chronically exposed to hypoxia, resting breathing frequency was significantly reduced (from 191±12 to 165±16 min–1); however, the ventilatory responses to hypoxia and hypercapnia were unaffected. Long-term exposure of fish to hypercapnic water did not markedly modify the breathing response to acute hypoxia and modestly blunted the response to hypercapnia.

To determine whether branchial chemoreceptors were being influenced by long-term acclimation, all four groups of fish were acutely exposed to increasing doses of the O2 chemoreceptor stimulant, sodium cyanide,dissolved in inspired water. Consistent with the blunting of the ventilatory response to hypoxia, the fish pre-exposed to hyperoxia also exhibited a blunted response to NaCN. Pre-exposure to hypoxia was without effect whereas prior exposure to hypercapnia increased the ventilatory responses to cyanide.

To assess the impact of acclimation to varying gas levels on branchial O2 chemoreceptors, the numbers of neuroepithelial cells (NECs) of the gill filament were quantified using confocal immunofluorescence microscopy. Consistent with the blunting of reflex ventilatory responses, fish exposed to chronic hyperoxia exhibited a significant decrease in the density of NECs from 36.8±2.8 to 22.7±2.3 filament–1.