bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystal symmetry and chemical composition of yukonite: TEM study of specimens collected from Nalychevskie hot springs, Kamchatka, Russia and from Venus Mine, Yukon Territory, Canada
Authors: Nishikawa O. , Okrugin V. , Belkova N. , Saji I. , Shiraki K. , Tazaki K.
Published: March 2006

Yukonite, a rare arsenic-bearing hydrous mineral, the crystal symmetry and variety in chemical composition of which have so far been insufficiently studied, has been found in the modern deposit of Nalychevskie hot springs in Central Kamchatka, Russia. This is the first finding of yukonite in Eastern Eurasia and Siberia. Yukonite specimens from Nalychevskie hot springs and from Venus Mine in Yukon Territory, Canada, have been investigated using an analytical transmission electron microscope (TEM). Yukonite is a crystalline substance with extremely thin (~5 nm) platy morphology. Yukonite from Venus Mine forms brittle aggregates in which grains are irregularly bent and randomly distributed. At Nalychevskie hot springs, yukonite occurs as single plates, coexisting with some amorphous material of similar composition. Intensity distributions in electron diffraction indicate that most plates of yukonite at Nalychevskie hot springs have orthorhombic symmetry, but some are hexagonal with ahex = 11.3 Å. The orthorhombic cell is C-centred with aorth = √3ahex, borth= ahex. High-resolution images of edge-on mounts indicate that the periodicity normal to the planes is d001=11.2 Å. Yukonite from Nalychevskie hot springs contains anomalously high Si relative to that in yukonite from Venus Mine and that reported previously. Strong negative correlation between As and Si indicates that Si substitutes for As in the structure.
Crystal structure of a synthetic aluminoan tantalian titanite: a reconnaissance study
Authors: Liferovich R. P. , Mitchell R. H.
Published: March 2006

A synthetic analogue, Ca(Ti0.6Al0.2Ta0.16Nb0.04)OSiO4, of an aluminoan tantalian titanite previously described from Craveggia pegmatite (Piemonte, Italy) has been prepared by a ceramic synthesis technique and its crystal structure determined by Rietveld analysis of the powder X-ray diffraction pattern. The synthetic Al-Ta-Nb-rich titanite adopts space groupA2/aimplying that substitutions at the single octahedral site destroy the coherence of the off-centering of octahedral chains in the titanite structure resulting in aP21/a →A2/aphase transition. Unit-cell dimensions obtained for the Al-Ta-Nb-rich titanite are:a =7.0649(1) Å;b =8.7187(1) Å;c =6.5701(1) Å; β = 113.755(1)°,V =370.41(1) Å3. The extensive replacement of Ti by Al, Ta and Nb results in a considerable decrease in the distortion of all coordination polyhedra in the structure of this titanite. These structural data suggest that a solid solution CaTi1-x(Alx/2[Ta,Nb]x/2)OSiO4(0 ≤x≤ 0.4) adopting the titanite structure might exist.
Kalungaite, PdAsSe, a new platinum-group mineral from the Buraco do Ouro gold mine, Cavalcante, Goiás State, Brazil
Authors: Botelho N. F. , Moura M. A. , Peterson R. C. , Stanley C. J. , Silva D. V. G.
Published: March 2006

Kalungaite, PdAsSe, is a new mineral discovered in the Buraco do Ouro gold mine, Cavalcante town, Goiás State, Brazil. It occurs in a quartz-muscovite mylonite, related to a peraluminous granite, in platy anhedral aggregates along foliation planes. Associated ore minerals are gold, chalcopyrite, bohdanowiczite, an unnamed Pb-Bi-Se-S mineral, clausthalite, guanajuatite, stibiopalladinite, sperrylite and padmaite. Gangue minerals are muscovite, quartz and rare tourmaline and magnetite. Kalungaite is lead-grey, has a metallic lustre, a black streak and is brittle with uneven fracture. No cleavage was observed. The mineral has a micro-indentation hardness of VHN25 = 438 (range of 429–455 kg/mm2 from five indentations). Under reflected light, kalungaite is cream, or creamy grey adjacent to gold grains, has no internal reflections and is isotropic. Reflectance values in air (and in oil) are: 47.5 (33.3) at 470 nm, 46.9 (32.6) at 546 nm, 46.8 (32.6) at 589 nm and 48.0 (34.0) at 650 nm. The average of eight electron-microprobe analyses gives: Pd 41.32, As 27.49, Bi 0.35, Sb 1.59, Se 27.67 and S 1.22, total 99.64 wt. %, corresponding to Pd1.006(As0.950Sb0.034Bi0.004)Σ0.988(Se0.908S0.099)Σ1.007Kalungaite is cubic, space group Pa, a = 6.089(4) Å, V = 225.78 Å3, Z = 4. Dcalc is 7.59 g/cm3. The strongest seven X-ray powder-diffraction lines [d in Å(I)(hkl )] are: 3.027(75)(002), 1.838(100)(113), 1.172(95)(115, 333), 1.077(80)(044, 144, 334), 0.988(70)(116, 235, 253), 0.929(90)(335) and 0.918(70)(226). Kalungaite is interpreted as having formed from hydrothermal fluids of granitic origin, during syn-emplacement shearing and alteration, producing an unusual gold-platinum-group element deposit.
Role of tumour necrosis factor-α receptor p75 in cigarette smoke-induced pulmonary inflammation and emphysema
Authors: D'hulst A. I. , Bracke K. R. , Maes T. , De Bleecker J. L. , Pauwels R. A. , Joos G. F. , Brusselle G. G.
Published: March 2006

Chronic obstructive pulmonary disease (COPD) is characterised by a local pulmonary inflammatory response to respiratory pollutants and by systemic inflammation. Tumour necrosis factor (TNF)-α has been implicated in systemic effects of COPD and operates by binding the p55 (R1) and p75 (R2) TNF-α receptors.

To investigate the contribution of each TNF-α receptor in the pathogenesis of COPD, the present study examined the effects of chronic air or cigarette smoke (CS) exposure in TNF-α R1 knockout (KO) mice, TNF-α R2 KO mice and wild type (WT) mice.

CS was found to significantly increase the protein levels of soluble TNF-α R1 (by four-fold) and TNF-α R2 (by 10-fold) in the bronchoalveolar lavage of WT mice. After 3 months, CS induced a prominent pulmonary inflammatory cell influx in WT and TNF-α R1 KO mice. In TNF-α R2 KO mice, CS-induced pulmonary inflammation was clearly attenuated. After 6 months, no emphysema was observed in CS-exposed TNF-α R2 KO mice in contrast to WT and TNF-α R1 KO mice. CS-exposed WT and TNF-α R1 KO mice failed to gain weight, whereas the body mass of TNF-α R2 KO mice was not affected.

These current findings suggest that both tumour necrosis factor-α receptors contribute to the pathogenesis of chronic obstructive pulmonary disease, but tumour necrosis factor-α receptor-2 is the most active receptor in the development of inflammation, emphysema and systemic weight loss in this murine model of chronic obstructive pulmonary disease.
Socio-economic status is related to incidence of asthma and respiratory symptoms in adults
Authors: Hedlund U. , Eriksson K. , Rönmark E.
Published: March 2006

The aim of the present study was to assess the association between socio-economic status and impaired respiratory health in a 10-yr follow-up of a population-based postal survey in Northern Sweden.

Multiple logistic regression was used to estimate odds ratios in relation to socio-economic class, using age, sex, a family history of asthma, smoking habits, and occupational exposures to dust, gases and fumes as possible confounders.

The study comprised 2,341 males and 2,413 females. Cumulative incidences were generally lowest in professionals, including executives and civil servants at intermediate and higher levels, who were chosen as reference group. Manual workers in industry showed a significantly increased risk of developing asthma, recurrent wheeze, attacks of shortness of breath or a combination of the two, and chronic productive cough. Manual workers in service showed a similar pattern for attacks of shortness of breath, recurrent wheeze, or a combination of the two, and chronic productive cough. The corresponding population attributable risks were ∼10%.

Low socio-economic status was a risk factor for the development of asthma, symptoms common in asthma and chronic productive cough.
Diagnoses of chronic beryllium disease within cohorts of sarcoidosis patients
Authors: Müller-Quernheim J. , Gaede K. I. , Fireman E. , Zissel G.
Published: March 2006

An increase in chronic beryllium disease (CBD) has been suggested due to higher industrial use of beryllium alloys. Since occupational CBD is a perfect phenocopy of sarcoidosis, it might be misdiagnosed as sarcoidosis. In the current it was hypothesised that CBD exists in cohorts of sarcoidosis patients.

In a prospective case study, sarcoidosis patients were evaluated for potential beryllium exposure. In those patients in whom beryllium exposure was confirmed and beryllium hypersensitivity demonstrated, the diagnosis of sarcoidosis was rejected and corrected to CBD.

In 84 patients seen for re-evaluation or making a diagnosis of sarcoidosis, beryllium exposure was recognised and a diagnosis of CBD was made in 34 out of 84 patients. The time lag between clinical diagnosis of sarcoidosis and the final diagnosis of CBD ranged 0–18 yrs (median 3 yrs) and the mean (range) age at time of diagnosis of CBD was 43.9(25–80) yrs. Beryllium-contaminated workplaces causing disease encompassed a wide spectrum of industries and technical trades in which beryllium-exposure is generally not perceived as a health hazard.

In conclusion, chronic beryllium disease still belongs to the spectrum of differential diagnoses of granulomatous disorders.
CC chemokine ligand 1 is released into the airways of atopic asthmatics
Authors: Montes-Vizuet R. , Vega-Miranda A. , Valencia-Maqueda E. , Negrete-García M. C. , Velásquez J. R. , Teran L. M.
Published: March 2006

CC chemokine ligand (CCL)1/I-309 is a potent attractant for T-helper cell type 2 lymphocytes. The present study investigates whether this cytokine is released in the bronchoalveolar fluid (BALF) of asthmatic patients.

Measurements of CCL1 using ELISA showed that levels of this cytokine were significantly elevated in BALF from asthmatics compared with normals (median (range) 193 (120–449) pg·mL−1versus30 (21–55) pg·mL−1). Differential cell counts in BALF showed that either lymphocyte or eosinophil numbers were elevated in asthmatic compared with normal subjects (10.8×103·mL−1versus1.0×103·mL−1and 1.7×103·mL−1versus0.2×103·mL−1, respectively). There was a trend towards a significant correlation between CCL1 levels and lymphocyte numbers in BALF. Separation of BALF using sequential CCL1 affinity column and reverse-phase high-performance liquid chromatography allowed detection of biologically active CCL1. Using immunohistochemistry, CCL1 immunoreactivity was localised predominantly to the airway epithelium.

Interestingly, there was a significant correlation between CC chemokine ligand 1 levels and epithelial cell numbers in bronchoalveolar lavage fluid and between these cells and lymphocyte numbers. Moreover, interleukin-4, interleukin-13 and interferon-γ stimulated primary bronchial airway epithelial cells to release CC chemokine ligand 1. These findings suggest that CC chemokine ligand 1 may play a role in lymphocyte recruitment in bronchial asthma.
Mesothelioma environment comprises cytokines and T-regulatory cells that suppress immune responses
Authors: Hegmans J. P. J. J. , Hemmes A. , Hammad H. , Boon L. , Hoogsteden H. C. , Lambrecht B. N.
Published: March 2006

Malignant mesothelioma is a cancer with dismal prognosis. The objective of the present study was to address the role of the immune system, tumour micro-environment and potential immunosuppression in mesothelioma.

Expression profiles of 80 cytokines were determined in the supernatant of mesothelioma cell lines and the original patient's pleural effusion. Influx of immune effector cells was detected by immunohistochemistry.

Angiogenin, vascular endothelial growth factor, transforming growth factor-β, epithelial neutrophil-activating protein-78 and several other proteins involved in immune suppression, angiogenesis and plasma extravasation could be detected in both supernatant and pleural effusion. Surrounding stroma and/or infiltrating cells were the most likely source of hepatocyte growth factor, macrophage inflammatory protein (MIP)-1δ, MIP-3α, neutrophil-activating peptide-2, and pulmonary and activation-regulated chemokine that can cause leukocyte infiltration and activation. There was a massive influx of CD4+ and CD8+ T-lymphocytes and macrophages, but not of dendritic cells, in human mesothelioma biopsies. It was further demonstrated that human mesothelioma tissue contained significant amounts of Foxp3+CD4+CD25+ regulatory T-cells. When these CD25+ regulatory T-cells were depleted in anin vivomouse model, survival increased.

Mesothelioma is infiltrated by immune effector cells but also contains cytokines and regulatory T-cells that suppress an efficient immune response. Immunotherapy of mesothelioma might be more effective when combined with drugs that eliminate or control regulatory T-cells.
On the relationship between induced polarization and surface area in metal-sand and clay-sand mixtures
Authors: Slater Lee , Ntarlagiannis Dimitrios , Wishart DeBonne
Published: March 2006

Induced polarization (IP) measurements were conducted on saturated kaolinite-, iron-, and magnetite-sand mixtures as a function of varying percentage weight of a mineral constituent: 0%–100% for iron and magnetite and 0%–32% for kaolinite. We determined the specific surface area for each mineral using nitrogen gas adsorption, where the porosity of each mixture was calculated from weight loss after drying. We fit a Cole-Cole model (Cole and Cole, 1941) to the electrical data obtained for the magnetite and iron mixtures. In contrast, the kaolinite mixtures showed a power-law dependence of phase-on frequency. The global polarization magnitude we obtained from the Cole-Cole modeling of the iron and magnetite mixtures displays a single, near-linear dependence on the ratio of surface area to pore volume ([Formula: see text]) calculated for the mixtures. A similar relationship is found using a local measure of polarization (imaginary conductivity at 1 Hz) for the clay-sand mixtures. The [Formula: see text] appears to be a critical parameter for determining IP in both metallic- and clay-containing soils. This result is not easily reconciled with traditional models of induced polarization.
Comparison between reprocessed seismic profiles: Seismologic and geologic data — A case study of the Colfiorito earthquake area
Authors: Stucchi Eusebio , Mirabella Francesco , Ciaccio Maria Grazia
Published: March 2006

Seismic reflection data are used to reconstruct the subsurface geologic structures below the Umbria-Marche region in Italy, a highly seismogenic area with a recent history of seismic activity (the 1997–1998 Colfiorito sequence). We reprocess three vibroseis seismic profiles (acquired in the early 1980s for hydrocarbon exploration) whose stacked sections were optimized for relatively deep oil targets. On the reprocessed seismic profile closest to the epicentral area, we construct the main reflectors to a depth of about 4 s (two-way time) and compare this interpretation with the available hypocenters of the 1997 earthquakes. The improvements in visualizing the shallow and deep reflections provide a better correlation between the reflectors and the observed surface structures as well as a better delineation of the basement-rock geometry. We find that part of the Colfiorito sequence is localized around some of the reflectors in the reflection profile, which we interpret as related to the active normal faults that outcrop at the surface.
A novel application of time-reversed acoustics: Salt-dome flank imaging using walkaway VSP surveys
Authors: Willis Mark E. , Lu Rongrong , Campman Xander , Nafi Toksöz M. , Zhang Yang , Hoop Maarten V. de
Published: March 2006

In this paper we present initial results of applying Time-Reversed Acoustics (TRA) technology to salt-dome flank, seismic imaging. We created a set of synthetic traces representing a multilevel, walkaway VSP for a model composed of a simplified Gulf of Mexico vertical-velocity gradient and an embedded salt dome. We first applied the concepts of TRA to the synthetic traces to create a set of redatummed traces without having to perform velocity analysis, moveout corrections, or complicated processing. Each redatummed trace approximates the output of a zero-offset, downhole source and receiver pair. To produce the final salt-dome flank image, we then applied conventional, poststack, depth migration to the zero-offset section. Our results show a very good image of the salt when compared to an image derived using data from a downhole, zero-offset source and receiver pairs. The simplicity of our TRA implementation provides a virtually automated method to estimate a zero-offset, seismic section as if it had been collected from the reference frame of the borehole containing the VSP survey.
A 3D subsalt tomography based on wave-equation migration-perturbation scans
Authors: Wang Bin , Dirks Volker , Guillaume Patrice , Audebert François , Epili Duryodhan
Published: March 2006

We have developed a simple but practical methodology for updating subsalt velocities using wave-equation, migration-perturbation scans. For the sake of economy and scalability (with respect to full source-receiver migration) and accuracy (with respect to common-azimuth migration), we use shot-profile, wave-equation migration. As input for subsalt-velocity analysis, we provide wave-equation migration scans with velocity scanning limited to the subsalt sediments. Throughout the migration-scan sections, we look for the best focusing or structural positioning of characteristic seismic events. The picking on the migration stacks selects the value of the best perturbation attribute (alpha-scaling factor) along with the corresponding position and local dip for the chosen seismic events. The associated, locally coherent events are then demigrated to the base of the salt horizon. Our key observation is that this process is theoretically equivalent to performing a datuming to a base of salt followed by subsalt migration of the redatumed data perturbed-velocity profiles. Thanks to this implicit redatuming of shot profiles, no ray tracing through the salt body is required. Thus, the events picked on the subsalt-velocity scans only need to be demigrated to the base of salt. For the event demigration we use 3D specular-ray tracing up to the base of the salt horizon within a predefined range of reflection angles. Event demigration produces model-independent data — time and time slope — that are then kinematically migrated using the current tomographic-inversion working model. To find a final-velocity model that will flatten best the remigrated events on common image point (CIP) angle gathers, we use the same set of demigrated observation data as the input data set for several nonlinear iterations of 3D tomographic inversion.
P-wave anisotropy from azimuthal AVO and velocity estimates using 3D seismic data from Saudi Arabia
Authors: Al-Marzoug Ahmed M. , Neves Fernando A. , Kim Jung J. , Nebrija Edgardo L.
Published: March 2006

A horizontal well is most productive in tight reservoirs when it intersects a large number of vertical fractures, yet strata near the borehole remain mechanically stable. Azimuthal velocity analysis and P-wave amplitude versus offset (AVO) using 3D wide-azimuth prestack surface seismic data provide a remote yet detailed way to map a fracture pattern away from well control. We estimate fracture direction and relative fracture intensity from such data at two gas fields in Saudi Arabia. Our results show a small azimuthal variation in P-wave velocity (maximum 5%) and a larger variation in azimuthal AVO at the reservoir (larger than 100%). Computed fracture attributes for field 1 show a consistent east-west fracture direction. However, in field 2, fracture azimuth is variable but generally east-west and north-south, with the strongly anisotropic north-south orientation correlating with faults and areas of large structural curvature in the reservoir. In both fields, azimuthal AVO analysis shows a more consistent estimate of fracture orientation than velocity analysis. These estimates have been instrumental in planning prolific and safe horizontal wells
Approximating spheroid inductive responses using spheres
Authors: Smith J. Torquil , Morrison H. Frank
Published: March 2006

Spheroid responses are important as limiting cases when modeling inductive responses of isolated metallic objects such as unexploded military ordnance. The response of high-permeability ([Formula: see text] ≥ 50) conductive spheroids of moderate aspect ratios (0.25–4) to excitation by uniform magnetic fields in the axial or transverse direction is approximated by the response of spheres of appropriate diameters, of the same conductivity and permeability, with magnitude rescaled based on the differing volumes, dc magnetizations, and high-frequency limit responses of the spheres and modelled spheroids. In the frequency domain, the scaled sphere responses agree within 5% of complex magnitudes for prolate spheroids and within 7% for oblate spheroids. The approximation is more accurate for source magnetic fields in the spheroid's shorter direction than in the spheroid's longer direction. In the time domain, the approximation describes spheroid responses over five decades of time after transmitter shutoff, with a maximum discrepancy of 20%.
Combining airborne electromagnetic data from alternating flight directions to form a virtual symmetric array
Authors: Smith Richard S. , Chouteau Michel C.
Published: March 2006

Fixed-wing towed-bird airborne electromagnetic (AEM) systems are asymmetric because the receiver flies behind and below the transmitter. As a consequence, the measured response is quite different when the aircraft flies a traverse line in the reverse direction, even when the causative bodies are symmetric. Because fixed-wing AEM survey traverses are parallel and are flown in alternating directions, the response of bodies can change markedly from one line to the next. This means that images of the measured data are complicated and difficult to interpret. In a survey in Quebec, Canada, each traverse line was flown twice, once in the normal direction and once in the reverse directions. These data were combined to give a response measured by a symmetric system termed the virtual symmetric array (VSA). The VSA response can enhance the S/N ratio, and the response will be symmetric if the con ductive targets are symmetric. Hence, any response asymmetry is indicative of asymmetry in the ground. This means that dip direction can be inferred from the VSA response. Images of VSA data show similar properties, making them a very useful tool for interpreting fixed-wing EM data. A field example is used to illustrate that the standard presentations (filtered images and energy envelope images) are smeared and blocky, whereas the VSA images show sharper resolution, better trending, and better subtle structural features on maps. In most cases, data are not collected in reverse-line directions, but it is possible to create an interpolated VSA image using the reverse line direction data from adjacent lines. When this process is applied to field data, the resulting images have all of the advantage of VSA images, except for somewhat lower S/N ratio improvements. Also, short strike-length features are elongated, and sudden changes in amplitude are not well imaged.
Robust 1D inversion and analysis of helicopter electromagnetic (HEM) data
Authors: Juhl Tølbøll Rasmus , Bøie Christensen Niels
Published: March 2006

Ground-based electrical and electromagnetic methods are used systematically for quantitative hydrogeologic investigations in Denmark. In recent years, a desire for faster and more cost-efficient methods has led to growing interest in the possibility of using airborne systems, and in 2001 a number of test flights were performed using a frequency-domain, helicopter-borne electromagnetic (HEM) system. We perform a theoretical examination of the resolution capabilities of the applied system. Quantitative model parameter analyses show that the system only weakly resolves conductive, near-surface layers but can resolve layer boundary to a depth of more than 100 m. Modeling experiments also show that the effect of altimeter errors on the inversion results is serious. We suggest a new interpretation scheme for HEM data founded solely on full nonlinear 1D inversion and providing layered-earth models supported by data misfit parameters and a quantitative model-parameter analysis. The backbone of the scheme is the removal of cultural coupling effects followed by a multilayer inversion that in turn provides reliable starting models for a subsequent few-layer inversion. A new procedure for correlation in the model space ensures model sections with slow lateral variations in resistivity, normally assumed in sedimentary environments. A field example from a Danish survey demonstrates that the interpretation scheme can produce satisfactory results within the limitations of the system.
Induced-polarization measurements on unconsolidated sediments from a site of active hydrocarbon biodegradation
Authors: Aal Gamal Z. Abdel , Slater Lee D. , Atekwana Estella A.
Published: March 2006

To investigate the potential role that indigenous microorganisms and microbial processes may play in altering lowfrequency electrical properties, induced-polarization (IP) measurements in the frequency range of 0.1 to 1000 Hz were acquired from sediment samples retrieved from a site contaminated by hydrocarbon undergoing intrinsic biodegradation. Increased imaginary conductivity and phase were observed for samples from the smear zone (contaminated with residual-phase hydrocarbon), exceeding values obtained for samples contaminated with dissolved-phase hydrocarbons, and in turn, exceeding values obtained for uncontaminated samples. Real conductivity, although generally elevated for samples from the smear zone, did not show a strong correlation with contamination. Controlled experiments on uncontaminated samples from the field site indicate that variations in surface area, electrolytic conductivity, and water content across the site cannot account for the high imaginary conductivity observed within the smear zone. We suggest that microbial processes may be responsible for the enhanced IP response observed at contaminated locations. Scanning electron microscopy and IP measurements during acid leaching indicate that etched pits on mineral surfaces — caused by the production of organic acids or formed during microbial colonization of these surfaces — are not the cause of the IP enhancement. Rather, we postulate that the accumulation of microbial cells (biofilms) with high surface area at the mineral-electrolyte interface generates the IP response. These findings illustrate the potential use of electrical measurements to noninvasively monitor microbial activity at sites undergoing natural hydrocarbon degradation.
Numerical simulation of antenna transmission and reception for crosshole ground-penetrating radar
Authors: Irving James D. , Knight Rosemary J.
Published: March 2006

Numerical models that account for realistic transmitter and receiver antenna behavior are necessary to develop waveform-based inversion methods for crosshole ground-penetrating radar (GPR) data. A challenge in developing such models is simulating the antennae in a computationally efficient manner so that inversions can be performed in a reasonable amount of time. We present an approach to efficiently simulate crosshole GPR transmission and reception in heterogeneous media. The core of our approach is a finite-difference time-domain (FDTD) solution of Maxwell's equations in 2D cylindrical coordinates. First, we determine the behavior of the current on a realistic GPR antenna in a borehole through detailed FDTD modeling of the antenna and its immediate surroundings. To model transmission and reception, we then replicate this antenna current behavior on a much-coarser grid using a superposition of point-electric-dipole source and receiver responses. Results obtained with our technique agree with analytical results, with numerical modeling results where the transmitter antenna and borehole are explicitly accounted for using a fine discretization, and with crosshole GPR field data.
Separation of magnetic-field data using the differential Markov random-field (DMRF) approach
Authors: Albora A. Muhittin , Uçan Osman N.
Published: March 2006

In this paper, the differential Markov random-field (DMRF) method is introduced and applied to the magnetic anomaly separation problem, in which residual anomalies are separated from a regional field. The DMRF method is an unsupervised statistical model-based learning approach that does not require prior knowledge. A data-adaptive program, based on the evaluation of noise and superimposed effects of various geologic structures, is presented by considering a statistical maximum a posteriori (MAP) criterion. The aim of our method is to capture the intrinsic properties of geologic structures and then to identify and hence understand the behavior of the observed magnetic-anomaly map. The magnetic-anomaly map is modeled using a 2D matrix. In the DMRF approach, each pixel of the matrix is evaluated considering neighboring pixels. In synthetic models, anomalies of magnetic dipoles are tested for different depths, orientation angles, and lengths. The DMRF method also is applied to the vertical magnetic-anomaly map of the Sivas-Divrigi region in Turkey, which contains the Dumluca iron ore reserves. Shallow reserves are detected clearly by the DMRF method, proving greater accuracy than classical filtering techniques. The results are confirmed by Technical Ore Research of Turkey (MTA) drilling reports.
A new elastic model for ground coupling of geophones with spikes
Authors: Drijkoningen Guy G. , Rademakers Frederik , Slob Evert C. , Fokkema Jacob T.
Published: March 2006

Ground coupling are terms that describe the transfer from seismic ground motion to the motion of a geophone. In previous models, ground coupling was mainly considered as a disk lying on top of a half-space, not considering the fact that in current practice geophones are spiked and are buried for optimal response. In this paper we introduce a new model that captures the spike added to the geophone and models the effect of geophone burial. The geophone is modeled as a rigid, movable cylinder embedded in a half-space near or at the surface. The coupling problem is then tackled by a scattering approach using the elastic form of reciprocity; we consider the vertical component only. The main feature in the coupling function is a resonance whose location and shape depend on the different parameters of the geophone and the soil. In accordance with previous models, adding mass reduces the frequency of resonance. However, we show that pure mass loading assumption is too restrictive for standard geophones. Our new model shows that increasing the spike radius and length decreases the frequency of resonance and the resonance is more peaked. Furthermore, burying the geophone decreases the frequency of resonance, but when one takes into account that the soil at depth is more compact, then the behavior is as observed in practice — namely, an increase in frequency of resonance. As for the properties of the soil, the shear-wave velocity has the largest effect; when increased, it shifts the frequency of resonance to the high-frequency end as desired.
Prestack migration deconvolution
Authors: Yu Jianhua , Hu Jianxing , Schuster Gerard T. , Estill Robert
Published: March 2006

Prestack migration in the time and depth domains is the premier tool for seismic imaging of complex structures. Unfortunately, an undersampled acquisition geometry, a limited recording aperture, and strong velocity contrasts lead to uneven illumination of the subsurface. This results in blurring the migrated image, sometimes referred to as acquisition footprint noise in the migrated image. To remedy this blurring partially, we introduce prestack migration deconvolution (MD). The MD filter is a layered-medium approximation to the inverse Hessian matrix that is applied locally to the migrated section. Both synthetic- and field-data results show noticeable improvements in reducing migration artifacts and increasing lateral spatial resolution by more than 10%. The computational expense for constructing the MD filter is related to the MD operator length. Its cost is about the same as that for migration, but opportunities exist for significantly reducing this cost. Results suggest that MD should be applied to migrated sections to optimize image quality.
Explicit 3D depth migration with a constrained operator
Authors: Mittet Rune
Published: March 2006

Numerical anisotropy is one of the main problems in the design of explicit 3D depth-extrapolation operators. This paper introduces a new method based on constraining the number of independent coefficients for the full 3D extrapolation operator. The extrapolation operator is divided into two regions. The coefficients for the inner part of the extrapolation operator are treated the same as the full 3D extrapolation operator. The coefficients for the outer part of the extrapolation operator are constrained to be constant as a function of azimuth for a given radius. This strategy reduces the number of floating-point operations because, for each extrapolation step, the number of complex multiplications are reduced and replaced by complex additions. The numerical workload of this alternative scheme is comparable to the Hale-McClellan scheme. Impulse responses are compared with finite-difference solutions for the two-way acoustic-wave equation. It is demonstrated that the numerical anisotropy for the proposed scheme is negligible and that the constrained-depth-extrapolation operator can be used in media with large lateral velocity contrasts. The design of constrained-depth-extrapolation operators with different maximum propagation angles in inline and crossline directions is explained and exemplified. These types of operators can be used to suppress the propagation of aliased energy in the crossline direction during depth extrapolation while reducing numerical cost.
Plane-wave propagation in attenuative transversely isotropic media
Authors: Zhu Yaping , Tsvankin Ilya
Published: March 2006

Directionally dependent attenuation in transversely isotropic (TI) media can influence significantly the body-wave amplitudes and distort the results of the AVO (amplitude variation with offset) analysis. Here, we develop a consistent analytic treatment of plane-wave properties for TI media with attenuation anisotropy. We use the concept of homogeneous wave propagation, assuming that in weakly attenuative media the real and imaginary parts of the wave vector are parallel to one another. The anisotropic quality factor can be described by matrix elements [Formula: see text], defined as the ratios of the real and imaginary parts of the corresponding stiffness coefficients. To characterize TI attenuation, we follow the idea of the Thomsen notation for velocity anisotropy and replace the components [Formula: see text] by two reference isotropic quantities and three dimensionless anisotropy parameters [Formula: see text], and [Formula: see text]. The parameters [Formula: see text] and [Formula: see text] quantify the difference between the horizontal- and vertical-attenuation coefficients of P- and SH-waves, respectively, while [Formula: see text] is defined through the second derivative of the P-wave attenuation coefficient in the symmetry direction. Although the definitions of [Formula: see text], and [Formula: see text] are similar to those for the corresponding Thomsen parameters, the expression for [Formula: see text] reflects the coupling between the attenuation and velocity anisotropy. Assuming weak attenuation as well as weak velocity and attenuation anisotropy allows us to obtain simple attenuation coefficients linearized in the Thomsen-style parameters. The normalized attenuation coefficients for P- and SV-waves have the same form as the corresponding approximate phase-velocity functions, but both [Formula: see text] and the effective SV-wave attenuation-anisotropy parameter [Formula: see text] depend on the velocity-anisotropy parameters in addition to the elements [Formula: see text]. The linearized approximations not only provide valuable analytic insight, but they also remain accurate for the practically important range of small and moderate anisotropy parameters — in particular, for near-vertical and near-horizontal propagation directions.
Amplitude, Fresnel zone, and NMO velocity for PP and SS normal-incidence reflections
Authors: Iversen Einar
Published: March 2006

Inspired by recent ray-theoretical developments, the theory of normal-incidence rays is generalized to accommodate P- and S-waves in layered isotropic and anisotropic media. The calculation of the three main factors contributing to the two-way amplitude — i.e., geometric spreading, phase shift from caustics, and accumulated reflection/transmission coefficients — is formulated as a recursive process in the upward direction of the normal-incidence rays. This step-by-step approach makes it possible to implement zero-offset amplitude modeling as an efficient one-way wavefront construction process. For the purpose of upward dynamic ray tracing, the one-way eigensolution matrix is introduced, having as minors the paraxial ray-tracing matrices for the wavefronts of two hypothetical waves, referred to by Hubral as the normal-incidence point (NIP) wave and the normal wave. Dynamic ray tracing expressed in terms of the one-way eigensolution matrix has two advantages: The formulas for geometric spreading, phase shift from caustics, and Fresnel zone matrix become particularly simple, and the amplitude and Fresnel zone matrix can be calculated without explicit knowledge of the interface curvatures at the point of normal-incidence reflection.
Intellectual Property
Authors: Walker David A.
Published: March 2006

The Intellectual Property department in each issue of Geophysics provides U.S. patent abstracts, published patent abstracts of U.S. patent applications, and published abstracts filed under the Patent Cooperation Treaty (PCT).
Velocity-porosity relationships, 1: Accurate velocity model for clean consolidated sandstones, GEOPHYSICS, 68, 1822–1834.
Authors: Knackstedt Mark A. , Arns Christoph H. , Pinczewski W. Val
Published: March 2006

The empirical equation of Arns et al., 2002a, is reproduced incorrectly in this paper as equation 22. The correct nonlinear empirical equation for the Poisson's ratio of a dry porous rock should read
Phase I study of docetaxel and topotecan in patients with advanced malignancies
Authors: Dubey Sarita , Hutson Paul , Alberti Dona , Arzoomanian Rhoda , Binger Kim , Volkman Jennifer , Feierabend Chris , Wilding George , Schiller Joan H
Published: March 2006

Background. Docetaxel and topotecan are drugs with different mechanisms of action and significant activity against various tumour types. Topotecan may influence docetaxel metabolism by inhibiting the CYP3A4 enzyme. We designed a phase I study to evaluate the maximum tolerated dose of this combination and to assess the impact of pharmaco-kinetic interactions of the two drugs on toxicity.

Methods. Docetaxel and topotecan were administered intravenously on day 1, and days 1- 5 respectively, using a phase I dose escalation design. Plasma samples were analysed to determine docetaxel and topotecan concentration by HPLC with subsequent pharmacokinetic analysis using NONMEM.

Results. Of the 17 patients enrolled in the trial, 11 had grade 3 and 4 neutropenia and 1 had grade 4 thrombocytopenia. Nonhaematological toxicities were less frequent. The maximum tolerated dose for docetaxel and topotecan were 60 mg/m2 on day 1 and 0.75 mg/m2 days 1- 5, respectively. One patient had stable disease. Subjects with grade]3 haematologic toxicity had higher plasma docetaxel or topotecan area under the curve (AUC) (docetaxel 1.0390.11 mg-hr/L versus 0.7390.13 mghr/L; topotecan 65.8914.6 mcg-hr/L versus 41.6913.9 mcg-hr/L). There was no additive effectoftheAUCofthetwodrugsonthe likelihood of grade]3 haematologic toxicity by multiple logistic regression.

Conclusion. The dose-limiting toxicity seen with the combination of docetaxel and topotecan was myelosuppression. Future trials will require growth factor support if this combination is pursued.
Actinic keratosis and capecitabine therapy
Authors: Higa Gerald M , Kovach Rodney F , Abraham Jame
Published: March 2006

Topical application of 5-fluorouracil (5-FU) is one of the most effective clinical strategies available to treat actinic keratosis (AK). During treatment, an apparent toxic skin reaction occurs before dermal quiescence ensues. We report a case of a typical flare of AK in a woman treated with capecitabine for advanced breast cancer.
Management of extravasation of oxaliplatin
Authors: de Lemos Mário L , Walisser Susan
Published: March 2006

Oxaliplatin extravasation has been associated with local pain and inflammation which may be severe and lead to complications including necrosis. Recent case reports suggest that oxaliplatin may be better classified as an irritant when extrava-sated. The optimal management of oxaliplatin extravasation however remains uncertain. Cold compress may cause local vasoconstriction and reduce cellular injury. However, it may potentially precipitate or worsen peripheral neuropathy. Warm compress may increase drug removal by local vasodilation and avoid peripheral neuropathy. However, it may potentially increase cellular uptake and hence injury. Further research into this area is needed.
FGF9 promotes survival of germ cells in the fetal testis
Authors: DiNapoli Leo , Batchvarov Jordan , Capel Blanche
Published: March 2006

In addition to its role in somatic cell development in the testis, our data have revealed a role for Fgf9 in XY germ cell survival. In Fgf9-null mice, germ cells in the XY gonad decline in numbers after 11.5 days post coitum (dpc), while germ cell numbers in XX gonads are unaffected. We present evidence that germ cells resident in the XY gonad become dependent on FGF9 signaling between 10.5 dpc and 11.5 dpc, and that FGF9 directly promotes XY gonocyte survival after 11.5 dpc, independently from Sertoli cell differentiation. Furthermore, XY Fgf9-null gonads undergo true male-to-female sex reversal as they initiate but fail to maintain the male pathway and subsequently express markers of ovarian differentiation(Fst and Bmp2). By 14.5 dpc, these gonads contain germ cells that enter meiosis synchronously with ovarian gonocytes. FGF9 is necessary for 11.5 dpc XY gonocyte survival and is the earliest reported factor with a sex-specific role in regulating germ cell survival.
FGF9 and SHH signaling coordinate lung growth and development through regulation of distinct mesenchymal domains
Authors: White Andrew C. , Xu Jingsong , Yin Yongjun , Smith Craig , Schmid Gregory , Ornitz David M.
Published: March 2006

Morphogenesis of the lung is regulated by reciprocal signaling between epithelium and mesenchyme. In previous studies, we have shown that FGF9 signals are essential for lung mesenchyme development. Using Fgf9loss-of-function and inducible gain-of-function mouse models, we show that lung mesenchyme can be divided into two distinct regions: the sub-mesothelial and sub-epithelial compartments, which proliferate in response to unique growth factor signals. Fibroblast growth factor (FGF) 9 signals from the mesothelium (the future pleura) to sub-mesothelial mesenchyme through both FGF receptor (FGFR) 1 and FGFR2 to induce proliferation. FGF9 also signals from the epithelium to the sub-epithelial mesenchyme to maintain SHH signaling,which regulates cell proliferation, survival and the expression of mesenchymal to epithelial signals. We further show that FGF9 represses peribronchiolar smooth muscle differentiation and stimulates vascular development in vivo. We propose a model in which FGF9 and SHH signals cooperate to regulate mesenchymal proliferation in distinct submesothelial and subepithelial regions. These data provide a molecular mechanism by which mesothelial and epithelial FGF9 directs lung development by regulating mesenchymal growth, and the pattern and expression levels of mesenchymal growth factors that signal back to the epithelium.
The first round of mouse spermatogenesis is a distinctive program that lacks the self-renewing spermatogonia stage
Authors: Yoshida Shosei , Sukeno Mamiko , Nakagawa Toshinori , Ohbo Kazuyuki , Nagamatsu Go , Suda Toshio , Nabeshima Yo-ichi
Published: March 2006

Mammalian spermatogenesis is maintained by a continuous supply of differentiating cells from self-renewing stem cells. The stem cell activity resides in a small subset of primitive germ cells, the undifferentiated spermatogonia. However, the relationship between the establishment of this population and the initiation of differentiation in the developing testes remains unclear. In this study, we have investigated this issue by using the unique expression of Ngn3, which is expressed specifically in the undifferentiated spermatogonia, but not in the differentiating spermatogonia or their progenitors, the gonocytes. Our lineage analyses demonstrate that the first round of mouse spermatogenesis initiates directly from gonocytes,without passing through the Ngn3-expressing stage (Ngn3- lineage). By contrast, the subsequent rounds of spermatogenesis are derived from Ngn3-positive undifferentiated spermatogonia, which are also immediate descendents of the gonocytes and represent the stem cell function(Ngn3+ lineage). Thus, in mouse spermatogenesis, the state of the undifferentiated spermatogonia is not an inevitable step but is a developmental option that ensures continuous sperm production. In addition,the segregation of gonocytes into undifferentiated spermatogonia(Ngn3+ lineage) or differentiating spermatogonia (Ngn3-lineage) is topographically related to the establishment of the seminiferous epithelial cycle, thus suggesting a role of somatic components in the establishment of stem cells.
spn-Fencodes a novel protein that affects oocyte patterning and bristle morphology inDrosophila
Authors: Abdu Uri , Bar Dikla , Schüpbach Trudi
Published: March 2006

The anteroposterior and dorsoventral axes of the Drosophila embryo are established during oogenesis through the activities of Gurken (Grk), a Tgfα-like protein, and the Epidermal growth factor receptor (Egfr). spn-F mutant females produce ventralized eggs similar to the phenotype produced by mutations in the grk-Egfr pathway. We found that the ventralization of the eggshell in spn-F mutants is due to defects in the localization and translation of grk mRNA during mid-oogenesis. Analysis of the microtubule network revealed defects in the organization of the microtubules around the oocyte nucleus. In addition, spn-F mutants have defective bristles. We cloned spn-F and found that it encodes a novel coiled-coil protein that localizes to the minus end of microtubules in the oocyte, and this localization requires the microtubule network and a Dynein heavy chain gene. We also show that Spn-F interacts directly with the Dynein light chain Ddlc-1. Our results show that we have identified a novel protein that affects oocyte axis determination and the organization of microtubules during Drosophila oogenesis.
Specification ofDrosophilaaCC motoneuron identity by a genetic cascade involvingeven-skipped, grainandzfh1
Authors: Garces Alain , Thor Stefan
Published: March 2006

During nervous system development, combinatorial codes of regulators act to specify different neuronal subclasses. However, within any given subclass,there exists a further refinement, apparent in Drosophila and C. elegans at single-cell resolution. The mechanisms that act to specify final and unique neuronal cell fates are still unclear. In the Drosophila embryo, one well-studied motoneuron subclass, the intersegmental motor nerve (ISN), consists of seven unique motoneurons. Specification of the ISN subclass is dependent upon both even-skipped(eve) and the zfh1 zinc-finger homeobox gene. We find that ISN motoneurons also express the GATA transcription factor Grain, and grn mutants display motor axon pathfinding defects. Although these three regulators are expressed by all ISN motoneurons, these genes act in an eve→grn→zfh1 genetic cascade unique to one of the ISN motoneurons, the aCC. Our results demonstrate that the specification of a unique neuron, within a given subclass, can be governed by a unique regulatory cascade of subclass determinants.