bluuebunny/crossref_metadata_2025 huggingface dataset:
Phenotypic features and genetic characterization of male breast cancer families: identification of two recurrent BRCA2 mutations in north-east of Italy
Authors: Miolo GianMaria , Puppa Lara Della , Santarosa Manuela , De Giacomi Clelia , Veronesi Andrea , Bidoli Ettore , Tibiletti Maria Grazia , Viel Alessandra , Dolcetti Riccardo
Published: June 2006

Background

Breast cancer in men is an infrequent occurrence, accounting for ~1% of all breast tumors with an incidence of about 1:100,000. The relative rarity of male breast cancer (MBC) limits our understanding of the epidemiologic, genetic and clinical features of this tumor.

Methods

From 1997 to 2003, 10 MBC patients were referred to our Institute for genetic counselling and BRCA1/2 testing. Here we report on the genetic and phenotypic characterization of 10 families with MBC from the North East of Italy. In particular, we wished to assess the occurrence of specific cancer types in relatives of MBC probands in families with and without BRCA2 predisposing mutations. Moreover, families with recurrent BRCA2 mutations were also characterized by haplotype analysis using 5 BRCA2-linked dinucleotide repeat markers and 8 intragenic BRCA2 polymorphisms.

Results

Two pathogenic mutations in the BRCA2 gene were observed: the 9106C>T (Q2960X) and the IVS16-2A>G (splicing) mutations, each in 2 cases. A BRCA1 mutation of uncertain significance 4590C>G (P1491A) was also observed. In families with BRCA2 mutations, female breast cancer was more frequent in the first and second-degree relatives compared to the families with wild type BRCA1/2 (31.9%vs. 8.0% p = 0.001). Reconstruction of the chromosome phasing in three families and the analysis of three isolated cases with the IVS16-2A>G BRCA2 mutation identified the same haplotype associated with MBC, supporting the possibility that this founder mutation previously detected in Slovenian families is also present in the North East of our Country. Moreover, analysis of one family with the 9106C>T BRCA2 mutation allowed the identification of common haplotypes for both microsatellite and intragenic polymorphisms segregating with the mutation. Three isolated cases with the same mutation shared the same intragenic polymorphisms and three 5' microsatellite markers, but showed a different haplotype for 3' markers, which were common to all three cases.

Conclusion

The 9106C>T and the IVS16-2A>G mutations constitute recurrent BRCA2 mutations in MBC cases from the North-East of Italy and may be associated with a founder effect. Knowledge of these two recurrent BRCA2 mutations predisposing to MBC may facilitate the analyses aimed at the identification of mutation carriers in our geographic area.
Characteristic abnormalities in cerebrospinal fluid biochemistry in children with cerebral malaria compared to viral encephalitis
Authors: Jakka SR , Veena S , Atmakuri RM , Eisenhut M
Published: June 2006

Background

In developing countries where Plasmodium falciparum malaria is endemic, viral encephalitis and cerebral malaria are found in the same population, and parasitemia with Plasmodium falciparum is common in asymptomatic children. The objective of this study was to investigate the cerebrospinal fluid (CSF) biochemistry in children with cerebral malaria compared to those with presumed viral encephalitis.

Methods

We studied the following CSF parameters: cell count, glucose, protein, lactic dehydrogenase (LDH) and adenosine deaminase (ADA) levels, in children with cerebral malaria, with presumed viral encephalitis, and in control subjects who had a lumbar puncture after a febrile convulsion with postictal coma.

Results

We recruited 12 children with cerebral malaria, 14 children with presumed viral encephalitis and 20 controls prospectively, over 2 years in the Government General Hospital in Kakinada, India. Patients with cerebral malaria had significantly lower CSF glucose, and higher protein, LDH, CSF/blood LDH ratio and CSF ADA levels but a lower CSF/serum ADA ratio compared to controls (p < 0.01). Patients with cerebral malaria had lower CSF white cell count, glucose, protein, LDH levels and CSF/serum ADA ratio compared to patients with presumed viral encephalitis. CSF/serum ADA ratio was lower in patients with cerebral malaria due to the fact that serum ADA levels were significantly higher in patients with cerebral malaria compared to the other two groups. A CSF/serum ADA ratio of <0.38 and a CSF glucose level of <3.4 mmol/l were selected as the cut-off values with the highest sensitivities and specificities for comparing the two conditions.

Conclusion

CSF/serum ADA ratio and CSF glucose levels were the best discriminators of cerebral malaria from presumed viral encephalitis in our study. Further studies are needed to explore their usefulness in epidemiological studies.
A method for determining gas-hydrate or free-gas saturation of porous media from seismic measurements
Authors: Zillmer Matthias
Published: June 2006

The occurrence of gas hydrate or free gas in a porous medium changes the medium’s elastic properties. Explicit formulas for gas-hydrate or free-gas saturation of pore space on the basis of the Frenkel-Gassmann equations describe the elastic moduli and seismic velocities of a porous medium for low frequencies. A key assumption of the model is that either gas hydrate or free gas is present in the pore space in addition to water. Under this assumption, the method uses measured P- and S-wave velocities and bulk density along with estimates of the moduli and densities of the solid and fluid phases present to determine whether gas or hydrate is present. The method then determines the saturation level of either the gas or the hydrate. I apply the method to published velocity and density data from seismic studies at the antarctic Shetland margin and at the Storegga slide, offshore Norway, and to borehole log and core data from Ocean Drilling Program (ODP) Leg 164 at Blake Ridge, offshore South Carolina. A sensitivity analysis reveals that the standard deviations of the gas-hydrate and free-gas saturations reach 30%–70% of the saturations if the standard deviations of the P- and S-wave velocities and of the bulk density are [Formula: see text] and [Formula: see text], respectively. I conclude that a reliable quantification of gas hydrate and free gas can be achieved by seismic methods only if the seismic velocities and bulk density of the medium are determined with high accuracy from the measured data.
Characterization of polarization attributes of seismic waves using continuous wavelet transforms
Authors: Diallo Mamadou S. , Kulesh Michail , Holschneider Matthias , Scherbaum Frank , Adler Frank
Published: June 2006

Complex-trace analysis is the method of choice for analyzing polarized data. Because particle motion can be represented by instantaneous attributes that show distinct features for waves of different polarization characteristics, it can be used to separate and characterize these waves. Traditional methods of complex-trace analysis only give the instantaneous attributes as a function of time or frequency. However, for transient wave types or seismic events that overlap in time, an estimate of the polarization parameters requires analysis of the time-frequency dependence of these attributes. We propose a method to map instantaneous polarization attributes of seismic signals in the wavelet domain and explicitly relate these attributes with the wavelet-transform coefficients of the analyzed signal. We compare our method with traditional complex-trace analysis using numerical examples. An advantage of our method is its possibility of performing the complete wave-mode separation/filtering process in the wavelet domain and its ability to provide the frequency dependence of ellipticity, which contains important information on the subsurface structure. Furthermore, using 2-C synthetic and real seismic shot gathers, we show how to use the method to separate different wave types and identify zones of interfering wave modes.
Joint inversion of gravity and magnetic data for two-layer models
Authors: Pilkington Mark
Published: June 2006

Gravity and magnetic data are inverted jointly in terms of a model consisting of an interface separating two layers having a constant density and magnetization contrast. A damped least-squares inversion is used to determine the topography of the interface. The inversion requires knowledge of the physical property contrasts across the interface and its average depth. Since the relationship between model parameters and data is weakly nonlinear, a constant damped least-squares inverse is used during the iterative solution search. The effect of this inverse is closely related to a downward continuation of the field to the average interface depth. The method is used to map the base of the Sept-Iles mafic intrusion, Quebec, Canada, and the shape of the central uplift at the Chicxulub impact crater, Yucatan, Mexico. At Sept-Iles, the intrusion reaches a thickness of [Formula: see text], coincident with the maximum gravity anomaly, south of the intrusion center. At Chicxulub, the top of the central uplift is modeled to be [Formula: see text] deep and has a single peak form.
3D surface-related multiple elimination: Data reconstruction and application to field data
Authors: Baumstein Anatoly , Hadidi Mohamed T.
Published: June 2006

The wide success of 2D surface-related multiple elimination (SRME) in attenuating complex multiples in many cases has spurred efforts to apply the method in three dimensions. However, application of 3D SRME to conventional marine data is often impeded by severe crossline aliasing characteristic of marine acquisition geometries. We propose to overcome this limitation using a dip-moveout (DMO)-based procedure consisting of the following steps: resorting the data into common offsets to improve crossline sampling, performing DMO to eliminate azimuth variations in the common-offset domain, and efficiently implementing inverse shot-record DMO to reconstruct densely sampled shot records required for 3D SRME to predict multiples correctly. We use a field data example to demonstrate that the proposed shot reconstruction procedure leads to kinematically accurate reconstruction of primaries but may not be able to simultaneously position multiples correctly. The mispositioning of multiples becomes a problem when second- and higher-order multiples must be predicted. We propose to resolve this difficulty by using a layer-stripping approach to multiple prediction. Alternatively, an approximate algorithm that relies on adaptive subtraction to compensate for inaccurate positioning of predicted multiples can be used. Application of the latter approach is illustrated with a field data example, and its performance is evaluated quantitatively through a measurement of S/N ratio improvement. We demonstrate that a DMO-based implementation of 3D SRME outperforms conventional 2D SRME and can accurately predict and attenuate complex 3D multiples.
Two ways to quantify uncertainty in geophysical inverse problems
Authors: Malinverno Alberto , Parker Robert L.
Published: June 2006

We present two approaches to invert geophysical measurements and estimate subsurface properties and their uncertainties when little is known a priori about the size of the errors associated with the data. We illustrate these approaches by inverting first-arrival traveltimes of seismic waves measured in a vertical well to infer the variation of compressional slowness in depth. First, we describe a Bayesian formulation based on probability distributions that define prior knowledge about the slowness and the data errors. We use an empirical Bayes approach, where hyperparameters are not well known ahead of time (e.g., the variance of the data errors) and are estimated from their most probable value, given the data. The second approach is a non-Bayesian formulation that we call spectral, in the sense that it uses the power spectral density of the traveltime data to constrain the inversion (e.g., to estimate the variance of the data errors). In the spectral approach, we vary assumptions made about the characteristics of the slowness signal and evaluate the resulting slowness estimates and their uncertainties. This approach is computationally simple and starts from a few assumptions. These assumptions can be checked during the analysis. On the other hand, it requires evenly spaced traveltime measurements, and it cannot be extended easily (e.g., to data that have gaps). In contrast, the Bayesian framework is based on a general theory that can be generalized immediately, but it is more involved computationally. Despite the conceptual and practical differences, we find that the two approaches give the same results when they start from the same assumptions: The allegiance to a Bayesian or non-Bayesian formulation matters less than what one is willing to assume when solving the inverse problem.
Refraction tomography using a waveform-inversion back-propagation technique
Authors: Min Dong-Joo , Shin Changsoo
Published: June 2006

One of the applications of refraction-traveltime tomography is to provide an initial model for waveform inversion and Kirchhoff prestack migration. For such applications, we need a refraction-traveltime tomography method that is robust for complicated and high-velocity-contrast models. Of the many refraction-traveltime tomography methods available, we believe wave-based algorithms to be best suited for dealing with complicated models.

We developed a new wave-based, refraction-tomography algorithm using a damped wave equation and a waveform-inversion back-propagation technique. The imaginary part of a complex angular frequency, which is generally introduced in frequency-domain wave modeling, acts as a damping factor. By choosing an optimal damping factor from the numerical-dispersion relation, we can suppress the wavetrains following the first arrival. The objective function of our algorithm consists of residuals between the respective phases of first arrivals in field data and in forward-modeled data. The model-response, first-arrival phases can be obtained by taking the natural logarithm of damped wavefields at a single frequency low enough to yield unwrapped phases, whereas field-data phases are generated by multiplying picked first-arrival traveltimes by the same angular frequency used to compute model-response phases.

To compute the steepest-descent direction, we apply a waveform-inversion back-propagation algorithm based on the symmetry of the Green’s function for the wave equation (i.e., the adjoint state of the wave equation), allowing us to avoid directly computing and saving sensitivities (Fréchet derivatives). From numerical examples of a block-anomaly model and the Marmousi-2 model, we confirm that traveltimes computed from a damped monochromatic wavefield are compatible with those picked from synthetic data, and our refraction-tomography method can provide initial models for Kirchhoff prestack depth migration.
Traveltime inversion of vertical radar profiles
Authors: Clement William P. , Knoll Michael D.
Published: June 2006

Traveltimes of direct arrivals in vertical radar profiles (VRPs) are tomographically inverted to estimate the earth’s electromagnetic (EM) velocity between a surface transmitter and a downhole receiver. We determine the 1D interval velocity model that best fits the first-arrival traveltimes by using a weighted, damped, least-squares inversion scheme. We assess the accuracy of the velocity model using synthetic traveltimes from a known velocity-distribution model simulating an unconfined aquifer. The inverted velocity profile closely matched the velocity profile of the input model in the synthetic examples. Using vertical radar profile data from an unconfined aquifer near Boise, Idaho, we inverted traveltimes to obtain velocity estimates at the well location. The velocity change at a depth of [Formula: see text] corresponds well with the measured depth to the water table of [Formula: see text], and at depths between 2 and [Formula: see text], the velocities ranged between 0.06 and [Formula: see text]. Our estimates approximately match the velocity distribution determined from neutron-derived porosity logs at depths greater than about [Formula: see text]. An important function of inverse methods is to assess (quantitatively and qualitatively) the uncertainty of inverted velocity estimates. We note that the velocity values in the upper and lower parts of the inverted model are not as well constrained compared to those between the depths of 4 and [Formula: see text]. From the model resolution and model covariance matrices of the real-data inversion, we determine the uncertainty in our velocity model, leading to more reliable interpretations of the subsurface.
QVOA analysis: P-wave attenuation anisotropy for fracture characterization
Authors: Chichinina Tatiana , Sabinin Vladimir , Ronquillo-Jarillo Gerardo
Published: June 2006

This paper investigates [Formula: see text]-anisotropy for characterizing fractured reservoirs — specifically, the variation of the seismic quality factor [Formula: see text] versus offset and azimuth (QVOA). We derive an analytical expression for P-wave attenuation in a transversely isotropic medium with horizontal symmetry axis (HTI) and provide a method (QVOA) for estimating fracture direction from azimuthally varying [Formula: see text] in PP-wave reflection data. The QVOA formula is similar to Rüger’s approximation for PP-wave reflection coefficients, the theoretical basis for amplitude variation with angle offset (AVOA) analysis. The technique for QVOA analysis is similar to azimuthal AVO analysis. We introduce two new seismic attributes: [Formula: see text] versus offset (QVO) gradient and intercept. QVO gradient inversion not only indicates fracture orientation but also characterizes [Formula: see text]-anisotropy. We relate the [Formula: see text]-anisotropy parameter [Formula: see text] to fractured-medium parameters and invert the QVO gradient to estimate [Formula: see text]. The attenuation parameter [Formula: see text] and Thomsen-style anisotropy parameter [Formula: see text] are found to be interdependent. The attenuation anisotropy magnitude strongly depends on the host rock’s [Formula: see text] parameter, whereas the dependence on fracture parameters is weak. This complicates the QVO gradient inversion for the fracture parameters. This result is independent of the attenuation mechanism. To illustrate the QVOA method in synthetic data, we use Hudson’s first-order effective-medium model of a dissipative fractured reservoir with fluid flow between aligned cracks and random pores as a possible mechanism for P-wave attenuation.
VTI anisotropic corrections and effective parameter estimation after isotropic prestack depth migration
Authors: Reshef Moshe , Roth Murray
Published: June 2006

In the method for applying anisotropic corrections after isotropic prestack depth migration (PSDM), the correction, which is calculated and implemented in the depth domain, is defined as a time difference between isotropic and anisotropic traveltimes, under the assumption that the vertical velocity is known. The definition of this correction uses a special postmigration common-image-gather (CIG) ordering, which collects the migrated data according to the input-trace’s source and receiver distance from the surface CIG location. In this postmigration domain, the dip of the events can be directly related to their horizontal position in the CIG, called the imaging offset, and the separation of flat and dipping reflectors becomes easy to perform. The dependency of the seismic anisotropic effect on the subsurface dip angle is well pronounced in these CIGs. After application of an isotropic PSDM, effective anisotropic-parameter estimation is performed at selected CIG locations by using a simple two-parameter scan procedure. The optimal anisotropic parameters can be used to perform a final anisotropic PSDM or to apply a residual correction to the isotropically migrated data. We demonstrate the method for P-wave data in 2D media with vertical transverse isotropy (VTI) symmetry by using both synthetic and real data. We also present a strategy for handling the ambiguity between the vertical velocity and the anisotropic parameters.
Fundamentals of the capacitive resistivity technique
Authors: Kuras Oliver , Beamish David , Meldrum Philip I. , Ogilvy Richard D.
Published: June 2006

Capacitive resistivity (CR) is an emerging geophysical technique designed to extend the scope of the conventional methodology of dc resistivity to environments where galvanic coupling is notoriously difficult to achieve — for example, across engineered structures (roads, pavements), hard rock, dry soil, or frozen ground. Conceptually, CR is based on a four-point array capacitively coupled to the ground. Under certain conditions, capacitive measurements of resistivity are equivalent to those obtained with the dc technique, thus making dc interpretation schemes applicable to CR data. The coupling properties of practical sensor realizations are shown to be a function of their geometrical arrangement. Separate bodies of theory are associated with two complementary but distinct sensor types: the capacitive-line antenna and the plate-wire combination. The use of plate-wire combinations results in localized coupling, which, in conjunction with a quasi-static (low-frequency) formulation of the transfer impedance, provides a valid emulation of the dc measurement with point electrodes.

A parametric study of the complex, quasi-static transfer impedance reveals the existence of a restricted range of practical parameters that permits successful operation of CR instruments at low induction numbers. Theory predicts that emulating the dc measurement is compromised if low-induction-number operation is not maintained throughout a survey area, as in a zone of high conductivity. Validation of the theory is achieved using specially designed field-scale experiments carried out with a CR instrument capable of measuring the full complex transfer impedance. At intermediate dipole separations, the results are consistent with the predictions of quasi-static theory. Deviations observed in the near and far separation zones can be explained by geometric effects or the breakdown of quasi-static conditions, respectively. Finally, under suitable conditions the phase-sensitive expression for apparent resistivity as a function of the complex transfer impedance is shown to reduce to the classical dc formula for the in-phase component. CR, while capable of emulating dc resistivity, also can be regarded as a physical complement of the inductively coupled ground-conductivity method.
Use of AVOA data to estimate fluid indicator in a vertically fractured medium
Authors: Shaw Ranjit K. , Sen Mrinal K.
Published: June 2006

Microstructural attributes of cracks and fractures, such as crack density, aspect ratio, and fluid infill, determine the elastic properties of a medium containing a set of parallel, vertical fractures. Although the tangential weakness [Formula: see text] of the fractures does not vary with the fluid content, the normal weakness [Formula: see text] exhibits significant dependence on fluid infill. Based on linear-slip theory, we used the ratio [Formula: see text] — termed the fluid indicator — as a quantitative measure of the fluid content in the fractures, with g representing the square of the ratio of S- and P-wave velocity in the unfractured medium. We used a Born formalism to derive the sensitivity to fracture weakness of PP- and PS-reflection coefficients for an interface separating an unfractured medium from a vertically fractured medium. Our formulae reveal that the PP-reflection coefficient does not depend on the 2D microcorrugation/surface roughness with ridges and valleys parallel to the fracture strike, whereas the PS-reflection coefficient is sensitive to this microstructural property of the fractures. Based on this formulation, we developed a method to compute the fluid indicator from wide-azimuth PP-AVOA data. Inversion of synthetic data corrupted with 10% random noise reliably estimates the normal and tangential fracture weaknesses and hence the fluid indicator can be determined accurately when the fractures are liquid-filled or partially saturated. As the gas saturation in the fractures increases, the quality of inversion becomes poorer. Errors of 15%–20% in g do not affect the estimation of fluid indicator significantly in case of liquid infill or partial saturation. However, for gas-saturated fractures, incorrect values of g may have a significant effect on fluid-indicator estimates.
Dip-scanning coherence algorithm using eigenstructure analysis and supertrace technique
Authors: Li Yandong , Lu Wenkai , Xiao Huanqin , Zhang Shanwen , Li Yanda
Published: June 2006

The eigenstructure-based coherence algorithms are robust to noise and able to produce enhanced coherence images. However, the original eigenstructure coherence algorithm does not implement dip scanning; therefore, it produces less satisfactory results in areas with strong structural dips. The supertrace technique also improves the coherence algorithms’ robustness by concatenating multiple seismic traces to form a supertrace. In addition, the supertrace data cube preserves the structural-dip information that is contained in the original seismic data cube; thus, dip scanning can be performed effectively using a number of adjacent supertraces. We combine the eigenstructure analysis and the dip-scanning supertrace technique to obtain a new coherence-estimation algorithm. Application to the real data set shows that the new algorithm provides good coherence estimates in areas with strong structural dips. Furthermore, the algorithm is computationally efficient because of the small covariance matrix [Formula: see text] used for the eigenstructure analysis.
Effects of spatially variable resolution on field-scale estimates of tracer concentration from electrical inversions using Archie’s law
Authors: Singha Kamini , Gorelick Steven M.
Published: June 2006

Two important mechanisms affect our ability to estimate solute concentrations quantitatively from the inversion of field-scale electrical resistivity tomography (ERT) data: (1) the spatially variable physical processes that govern the flow of current as well as the variation of physical properties in space and (2) the overparameterization of inverse models, which requires the imposition of a smoothing constraint (regularization) to facilitate convergence of the inverse solution. Based on analyses of field and synthetic data, we find that the ability of ERT to recover the 3D shape and magnitudes of a migrating conductive target is spatially variable. Additionally, the application of Archie’s law to tomograms from field ERT data produced solute concentrations that are consistently less than 10% of point measurements collected in the field and estimated from transport modeling. Estimates of concentration from ERT using Archie’s law only fit measured solute concentrations if the apparent formation factor is varied with space and time and allowed to take on unreasonably high values. Our analysis suggests that the inability to find a single petrophysical relation in space and time between concentration and electrical resistivity is largely an effect of two properties of ERT surveys: (1) decreased sensitivity of ERT to detect the target plume with increasing distance from the electrodes and (2) the smoothing imprint of regularization used in inversion.
Large-scale geophysical reconstruction of man-made ground at former industrial iron-furnace plantations
Authors: Kulessa Bernd , Chiarulli Beverly , McCarthy Paul , Haney Susanne , Jones Kevin
Published: June 2006

Blast-iron-furnace plantations were widespread throughout colonial and postcolonial America and therefore represent sites of specific archaeological interest. Because such plantations often were a really extensive, historical reconstruction of a site is challenging using conventional archaeological field techniques alone. Therefore, we appraise the usefulness of integrating magnetic gradiometer, electrical-resistivity tomography (ERT), and electromagnetic (EM31) data in detecting and delineating buried structures related to former operation of the Shade furnace, a typical industrial plantation in 19th-century Pennsylvania. The geophysical results were ground-truthed in seven locations by archaeological excavation. Geophysical results demonstrated that (1) the distribution of remaining original soils could be mapped; (2) waste materials (e.g., slag, used brick, burned charcoal, iron ore, and broken-up sandstone or limestone) within or above the original soils could be detected and delineated, whether the material occurred in pits or lenses or was dispersed across the ground surface; and (3) the location and spatial extent of many former structures related to furnace operation could be identified, such as building or bridge foundations and casting-related structures (e.g., the tapping channel or the casting floor, and the former courses of a water canal (raceway) and a supply road). We conclude that geophysical techniques can play a key role in reconstructing man-made ground at former industrial furnace sites in North America.
Theory of borehole stability when drilling through salt formations
Authors: Carcione José M. , Helle Hans B. , Gangi Anthony F.
Published: June 2006

We present a mathematical analysis of borehole stability when drilling through rock salt. First, we consider an elastic transversely isotropic medium and find the optimal mud weight as a function of the vertical overburden and horizontal tectonic stresses. Then, the Zener and Maxwell mechanical models are used to model the effects of transient and steady-state creep flow, respectively, in isotropic media. Under certain conditions such as the absence of dilatational anelasticity, the Burger model can be used to describe the steady-state flow, including transient creep effects. The type of creep is regulated by critical octahedral-stress values that depend on temperature and pressure. A typical drilling results in conditions of plane strain, whose solution is given by Kirsch’s equations. In this case, the borehole is subject to minimum and maximum horizontal stresses, which differ from the vertical stress. The analysis provides expressions for the shape of the borehole-cross section, the borehole-wall closure time, and the optimal mud weight to avoid wall collapse or expansion. It is shown that an anisotropic state of tectonic stress may require mud pressures exceeding the overburden stress and that the calculation should consider the joint optimization of the shape and area of the borehole cross section.
Determining capillary-pressure curve, pore-size distribution, and permeability from induced polarization of shaley sand
Authors: Tong Maosong , Li Li , Wang Weinan , Jiang Yizhong
Published: June 2006

An appropriate form of induced polarization (IP) acts as a bridge between the structure of a water-saturated core plug and its transport properties. The induced-polarization decay curves of natural rocks can be modeled as a weighted superposition of exponential relaxations. A singular-value decomposition method makes it possible to transform the induced-polarization decay data of the shaley sands into relaxation-time spectrum, defined as plot of weight versus the relaxation-time constant. We measured the induced-polarization decay curves of core samples from a formation of Daqing oil field using a four-electrode method. The decay curves were transformed to relaxation-time spectra that were used to estimate the capillary-pressure curves, the pore-size distribution, and the permeability of the shaley sands. The results show that salinity ranges from [Formula: see text] have little effect on the IP relaxation-time spectra. A pseudocapillary pressure curve can be derived from the IP relaxation-time spectrum by matching the pseudocapillary curve with that from HgAir. The best-matching coefficients of the studied cores change slightly for the samples. Defined as the value of pressure at which the injected mercury saturation is 5%, entry pressures of the cores can be estimated well from IP-derived capillary-pressure curves. Pore-size distributions generated from induced polarization and mercury capillary-pressure curves are comparable. Permeability can be predicted from IP measurements in the form of [Formula: see text], where [Formula: see text] is the estimated permeability from IP relaxation spectrum in millidarcies (md), [Formula: see text] is the porosity in percentage, and [Formula: see text] is average time constant of IP relaxation-time spectra in millis (ms). The constants and exponents from various rock formations are slightly different.
Improving explicit seismic depth migration with a stabilizing Wiener filter and spatial resampling
Authors: Margrave Gary F. , Geiger Hugh D. , Al-Saleh Saleh M. , Lamoureux Michael P.
Published: June 2006

We present a new approach to the design and implementation of explicit wavefield extrapolation for seismic depth migration in the space-frequency domain. Instability of the wavefield extrapolation operator is addressed by splitting the operator into two parts, one to control phase accuracy and a second to improve stability. The first partial operator is simply a windowed version of the exact operator for a half step. The second partial operator is designed, using the Wiener filter method, as a band-limited, least-squares inverse of the first. The final wavefield extrapolation operator for a full step is formed as a convolution of the first partial operator with the complex conjugate of the second. This resulting wavefield extrapolation operator can be designed to have any desired length and is generally more stable and more accurate than a simple windowed operator of similar length. Additional stability is gained by reducing the amount of evanescent filtering and by spatially downsampling the lower temporal frequencies. The amount of evanescent filtering is controlled by building two operator tables, one corresponding to significant evanescent filtering and the other to very little evanescent filtering. During the wavefield extrapolation process, most steps are taken with the second table while the first is invoked only for roughly every tenth step. Also, the data are divided into frequency partitions that are optimally resampled in the spatial coordinates to further enhance the performance of the extrapolation operator. Lower frequencies are downsampled to a larger spatial sample size. Testing of the algorithm shows accurate, high-angle impulse responses and run times comparable to the phase shift method of time migration. Images from trial depth migrations of the Marmousi model show very high resolution.
Seismic characterization of multiple fracture sets: Does orthotropy suffice?
Authors: Grechka Vladimir , Kachanov Mark
Published: June 2006

As geophysicists rely increasingly on effective media theories to characterize naturally fractured reservoirs, they become more and more interested in evaluating the accuracy of different theories, estimating their limits of applicability, and assessing their usefulness for practice. With this in mind, we compare two popular seismological theories of Hudson and Schoenberg with the theory of Kachanov developed in the context of mechanics of materials. By performing finite-element simulations of effective media for models that contain several sets of nonintersecting, circular, vertical fractures embedded in otherwise isotropic host rock, we examine the accuracy of these theories. Our numeric study reveals that predictions of both the first- and second-order Hudson's theories are typically inferior to those of others, especially when the fractures are dry. While, on average, the theories of Schoenberg and Kachanov fit finite-element computations with comparable accuracy, the latter appears to be more useful for fracture characterization. The reason is thatit correctly predicts the proximity of crack-induced anisotropy to orthotropy, whereas the other theories do not. Kachanov's results not only yield approximate effective orthotropy regardless of the number of fracture sets, their crack densities, and orientations, but they also lead to a substantially reduced number of independent parameters that govern the effective stiffnesses. This number is only four for dry cracks, compared to nine required for general orthorhombic media. These four quantities can be chosen as two Lamé constants of the isotropic background and two principal crack densities. If fractures are filled with a compressible fluid, the number of independent parameters increases. After numeric verification of the accuracy of crack-induced orthotropy, we invert the NMO ellipses and zero-offset traveltimes of P-waves and two split shear waves for the parameters characterizing multiple fracture sets. Our inversion reveals the fracture parameters that can be unambiguously estimated from multiazimuth, multicomponent surface reflection data.
2.5D resistivity modeling of embankment dams to assess influence from geometry and material properties
Authors: Sjödahl Pontus , Dahlin Torleif , Zhou Bing
Published: June 2006

Repeated resistivity measurement is a potentially powerful method for monitoring development of internal erosion and anomalous seepage in earth embankment dams. This study is part of a project to improve current longterm monitoring routines and data interpretation and increasing the understanding when interpreting existing data. This is accomplished by modeling various occurrences typical of embankment structures using properties from two rockfill embankment dams with central till cores in the north of Sweden. The study evaluates the influence from 3D effects created by specific dam geometry and effects of water level fluctuations in the reservoir. Moreover, a comparison between different layout locations is carried out, and detectability of internal erosion scenarios is estimated through modeling of simulated damage situations. Software was especially developed to model apparent resistivity for geometries and material distributions for embankment dams. The model shows that the 3D effect from the embankment geometry is clearly significant when measuring along dam crests. For dams constructed with a conductive core of fine-grained soil and high-resistive rockfill, the effect becomes greatly enhanced. Also, water level fluctuations have a clear effect on apparent resistivities. Only small differences were found between the investigated arrays. A layout along the top of the crest is optimal for monitoring on existing dams, where intrusive investigations are normally avoided, because it is important to pass the current through the conductive core, which is often the main target of investigation. The investigation technique has proven beneficial for improving monitoring routines and increasing the understanding of results from the ongoing monitoring programs. Although the technique and software are developed for dam modeling, it could be used for estimation of 3D influence on any elongated structure with a 2D cross section.
The Expression of Aromatase in Gonadotropes Is Regulated by Estradiol and Gonadotropin-Releasing Hormone in a Manner that Differs from the Regulation of Luteinizing Hormone
Authors: Galmiche Guillaume , Richard Nicolas , Corvaisier Sophie , Kottler Marie-Laure
Published: June 2006

The role of estrogens is dual: they suppress basal expression of gonadotropins and enhance GnRH responsiveness at the time of the LH surge. Estrogens are synthesized by cytochrome P450 aromatase (P450arom), encoded by the cyp19 gene. We focused on the cyp19 gene in rat and showed that it is expressed in gonadotropes through promoters PII and PI.f, using RT-PCR and dual fluorescence labeling with anti-P450arom and -LH antibodies. Real-time PCR quantification revealed that aromatase mRNA levels varied during the estrous cycle and were significantly increased after ovariectomy. This effect is prevented by estradiol (E2) as well as GnRH antagonist administration, suggesting that GnRH may mediate the steroid effect. Interestingly, the long-acting GnRH agonist that induces LH desensitization does not modify aromatase expression in ovariectomized rats. Administration of E2 in ovariectomized rats receiving either GnRH agonist or GnRH antagonist clearly demonstrated that E2 also reduces cyp19 expression at the pituitary level. The selective estrogen receptor-α ligand propyl pyrazole triol and the selective estrogen receptor-β ligand diarylpropionitrile both mimic the E2 effects. By contrast, propyl pyrazole triol reduces LHβ expression whereas diarylpropionitrile does not. In addition, using transient transfection assays in an LβT2 gonadotrope cell line, we provided evidence that GnRH agonist stimulated, in a dose-dependant manner, cyp19 promoters PII and PI.f and that E2 decreased the GnRH stimulation. In conclusion, our data demonstrate that GnRH is an important signal in the regulation of cyp19 in gonadotrope cells. Both common and specific intracellular factors were responsible for dissociated variations of LHβ and cyp19 expression.
The Endocrine-Gland-Derived Vascular Endothelial Growth Factor (EG-VEGF)/Prokineticin 1 and 2 and Receptor Expression in Human Prostate: Up-Regulation of EG-VEGF/Prokineticin 1 with Malignancy
Authors: Pasquali Daniela , Rossi Valentina , Staibano Stefania , De Rosa Gaetano , Chieffi Paolo , Prezioso Domenico , Mirone Vincenzo , Mascolo Massimo , Tramontano Donatella , Bellastella Antonio , Sinisi Antonio Agostino
Published: June 2006

A new family of angiogenic factors named endocrine-gland-derived vascular endothelial growth factors (EG-VEGF)/prokineticins (PK) have been recently described as predominantly expressed in steroidogenic tissues. Whether the normal and malignant epithelial prostate cells and tissues express EG-VEGF/PK1 and PK2 and their receptors is still unknown. We studied the expression of EG-VEGF/PK1 and PK2 and their receptors (PK-R1 and PK-R2) in human prostate and their involvement in cancer. Using immunohistochemistry, Western blot, and RT-PCR, we determined the expression of EG-VEGF/PK1 in normal prostate (NP) and malignant prostate tissues (PCa), in epithelial cell primary cultures from normal prostate (NPEC) and malignant prostate (CPEC) and in a panel of prostate cell lines. In NPEC, CPEC, and in EPN, a nontransformed human prostate epithelial cell line, EG-VEGF/PK1, PK2, PK-R1, and PK-R2 mRNA levels were evaluated by quantitative RT-PCR. EG-VEGF/PK1 transcript was found in PCa, in CPEC, in EPN, and in LNCaP, whereas it was detected at low level in NP and in NPEC. EG-VEGF/PK1 was absent in androgen-independent PC3 and DU-145 cell lines. Immunochemistry confirmed that EG-VEGF/PK1 protein expression was restricted to hyperplastic and malignant prostate tissues, localized in the glandular epithelial cells, and progressively increased with the prostate cancer Gleason score advancement. EG-VEGF/PK1 and PK2 were weakly expressed in NPEC and EPN. On the other hand, their transcripts were highly detected in CPEC. PK-R1 and PK-R2 were found in NPEC, EPN, and CPEC. Interestingly, CPEC showed a significantly (P < 0.05) higher expression of EG-VEGF/PK1, PK2, PK-R1, and PK-R2 compared with NPEC and EPN. We demonstrated that PKs and their receptors are expressed in human prostate and that their levels increased with prostate malignancy. It may imply that EG-VEGF/PK1 could be involved in prostate carcinogenesis, probably regulating angiogenesis. Thus, the level of EG-VEGF/PK1 could be useful for prostate cancer outcome evaluation and as a target for prostate cancer treatment in the future.
An Intact N Terminus Is Required for the Anabolic Action of Parathyroid Hormone on Adult Female Rats
Authors: Armamento-Villareal Reina , Ziambaras Konstantinos , Abbasi-Jarhomi S. Hasan , Dimarogonas Andrew , Halstead Linda , Fausto Aurora , Avioli Louis V. , Civitelli Roberto
Published: June 2006

Intermittent administration of parathyroid hormone (PTH) peptides increases bone density in animal and human models of osteoporosis. In vitro studies have demonstrated that PTH analogs lacking the first two amino acids can stimulate cell proliferation in certain cell systems, whereas fragments with an intact N terminus can be antimitogenic. We have tested whether the truncated PTH(3–38) fragment may be a better “anabolic analog” than PTH(1–38) by monitoring bone density and biomechanical properties of the femur in 6-month-old ovariectomized (OVX) rats. Either PTH fragment was administered subcutaneously (8 μg/100 g of body weight) 5 days/week, for 4 weeks, starting 1 week after surgery. During the entire study, untreated OVX rats lost 12.1 ± 4.4% of their initial bone density. PTH(1–38) reversed the initial bone loss, leading to complete restoration of presurgery values after 4 weeks of treatment. Conversely, administration of PTH(3–38) resulted in 13.2 ± 5.8% bone loss, while continuous estrogen infusion (10 μg/kg/day) prevented bone loss but did not reverse it. Sham-operated animals also experienced significant bone loss in the vehicle and PTH(3–38)–treated groups (−4.5 ± 6.7%, and −7.6 ± 2.8%, respectively), whereas a significant gain in bone density (+4.4 ± 5.6%) was observed in the rats treated with PTH(1–38). A bone quality factor (index of strain energy loss) and the impact strength (resistance to fracture) were 25% and 44% lower in femurs explanted from OVX a0nimals treated with either vehicle or PTH(3–38), compared with sham-operated animals. On the contrary, no difference was observed between OVX and control animals after treatment with PTH(1–38), indicating a preservation of the capacity to withstand mechanical stress. Thus, PTH(1–38) counteracts estrogen-dependent loss of mineral density and bone biomechanical properties and increases bone density in estrogen-replete animals. An intact N terminus sequence is necessary for this anabolic action of PTH.
A Distinct Cation-Sensing Mechanism in MC3T3-E1 Osteoblasts Functionally Related to the Calcium Receptor
Authors: Quarles L. Darryl , Hartle James E. , Siddhanti Suresh R. , Guo Rong , Hinson Todd K.
Published: June 2006

The presence of a cation-sensing mechanism in osteoblasts is suggested by the ability of specific cations to stimulate osteoblastic proliferation in culture and to induce de novo bone formation in some experimental models. Our study examines whether extracellular cations stimulate osteoblasts through the recently identified G protein–coupled calcium receptor (CaR). We found that CaR agonists, calcium (Ca2+), gadolinium (Gd3+), aluminum (Al3+), and neomycin, stimulated DNA synthesis in murine-derived MC3T3-E1 preosteoblasts, whereas magnesium (Mg2+), nickel (Ni2+), cadmium (Cd2+), and zinc (Zn2+) had no effect. With the exception of Mg2+, the cation specificities and apparent affinities were similar to that reported for CaR. CaR agonists also stimulated DNA synthesis in C3HT101/2 fibroblasts, but not in mesangial PVG, CHO, hepatic HTC, COS-7 cells, or malignant transformed ROS17/2.8 and UMR-106 osteoblasts. In addition, similar to other growth factors, CaR agonists activated transcription of a serum response element luciferase reporter construct (SRE-Luc) stably transfected into MC3T3-E1 osteoblasts, but had no effect on SRE-Luc transfected into CHO and COS-7 cells. We were unable to detect CaR expression by Northern analysis using a mouse CaR-specific probe or to amplify CaR mRNA by reverse transcribed polymerase chain reaction in MC3T3-E1 osteoblasts. These findings suggest that an extracellular cation-sensing mechanism is present in murine-derived osteoblasts that is functionally similar to but molecularly distinct from CaR.