bluuebunny/crossref_metadata_2025 huggingface dataset:
Perturbation of B-cell development in mice overexpressing the Bcl-2 homolog A1
Authors: Chuang Peter I. , Morefield Samantha , Liu Chien-Ying , Chen Stephen , Harlan John M. , Willerford Dennis M.
Published: October 2002

Decisions about cell survival or death are central components of adaptive immunity and occur at several levels in immune system development and function. The Bcl-2 family of homologous proteins plays an important role in these decisions in lymphoid cells. Bcl-2, Bcl-xL, and A1 are differentially expressed during B- and T-cell development, and they have shared and distinct roles in regulating cell death. We sought to gain insight into the role of A1 in immune system development and function. A murine A1-a transgene was expressed under the control of the Eμ enhancer, and mice with A1 overexpression in B- and T-cell lineages were derived. Thymocytes and early B cells in Eμ-A1 mice showed extended survival. B-lineage development was altered, with expansion of the pro–B cell subset at the expense of pre–B cells, suggesting an impairment of the pro– to pre–B-cell transition. This early B-cell phenotype resembled Eμ–Bcl-xL mice but did not preferentially rescue cells with completed V(D)J rearrangements of the immunoglobulin heavy chain. In contrast to Eμ–Bcl-2 transgenes, A1 expression in pro–B cells did not rescue pre–B-cell development in SCID mice. These studies indicate that A1 protects lymphocytes from apoptosis in vitro but that it has lineage- and stage-specific effects on lymphoid development. Comparison with the effects of Bcl-2 and Bcl-xL expressed under similar control elements supports the model that antiapoptotic Bcl-2 homologs interact differentially with intracellular pathways affecting development and apoptosis in lymphoid cells.
In situ localization of follicular lymphoma: description and analysis by laser capture microdissection
Authors: Cong Peijie , Raffeld Mark , Teruya-Feldstein Julie , Sorbara Lynn , Pittaluga Stefania , Jaffe Elaine S.
Published: October 2002

From 1992 to 2000, we identified 23 lymph node biopsies with focal germinal centers (GCs) containing centrocytes staining strongly for bcl-2 protein, whereas most of the remaining lymph node showed bcl-2–negative follicular hyperplasia. We propose the designation in situ localization of follicular lymphoma (FL) for this phenomenon. In 2 additional cases, bcl-2+ follicles with features of in situ FL were identified in association with other low-grade B-cell lymphomas. To investigate the clonality of the bcl-2+follicles, we performed laser capture microdissection of bcl-2+ and bcl-2 follicles from the same lymph node in 5 cases, and analyzed them in parallel by polymerase chain reaction (PCR) amplification of immunoglobulin heavy chain (IgH) genes. In 4 of 5 cases the bcl-2+ follicles contained monoclonal IgH gene rearrangements, whereas the bcl-2− GCs exhibited a polyclonal ladder. A BCL2/JH gene rearrangement was detected in 6 of 14 (43%) evaluable cases. There were 5 patients with synchronous evidence of FL at another site. There were 13 patients who, without a prior diagnosis of FL, had clinical follow-up; one developed FL in an adjacent lymph node within one year, and 2 manifested FL at 13 and 72 months, respectively. There are 10 patients who have not yet shown other evidence of FL. These results suggest that at least close to half of these cases (8/18; 44%) represent homing to and early colonization of reactive GCs by FL. Other cases might represent FL at the earliest stage of development, or a preneoplastic event, requiring a second hit for neoplastic transformation. These findings provide insight into the pathophysiology of early FL, and illustrate the utility of immunohistochemistry for early diagnosis.
A LINE‐INTEGRAL METHOD OF COMPUTING THE GRAVIMETRIC EFFECTS OF TWO‐DIMENSIONAL MASSES
Authors: Hubbert M. King
Published: October 2002

Many computing schemes have been devised for determining the gravity anomalies produced by two‐dimensional masses. Most of these are based upon the evaluation of an areal integral and require specially constructed templates or tables. In the present paper it is shown that the gravity anomaly Δg at the origin of coordinates, produced by a two‐dimensional mass of constant density contrast Δρ, may be obtained quite simply by means of either of the line integrals [Formula: see text] where z is the vertical coordinate, and θ the polar coordinate expressed in radians of a point on the periphery of the mass in a plane normal to its axis and passing through the origin. The line integrals are evaluated around the periphery of the mass and are of opposite sign if taken in the same direction of traverse, or are of the same sign if taken in opposite directions. For use of these integrals no special equipment is required other than a simple template consisting of radial lines, θ=const., and horizontal lines, z=const., which can be constructed in a few minutes with protractor and scale. This can be constructed either for 1:1 or for an exaggerated vertical‐to‐horizontal scale.
SOME LIMITING FACTORS AND PROBLEMS OF MINING GEOPHYSICS
Authors: Brant A. A.
Published: October 2002

The force‐field methods, magnetic, electrical resistivity and equipotential, self‐potential, electromagnetic, gravimetric and geothermal, where the forces observed result from the action of natural or artificial fields are all limited by the decrease in anomaly according to an inverse power law with the depth of the anomalous body. Furthermore large physical‐property contrasts frequently occur in the surface material, making the detection and interpretation of subsurface conditions difficult. The mining structures controlling ore deposition are small, measuring the order of feet to hundreds of feet, and are manifold in number. The direct detection of ore is seldom possible. A more accurate assessing of the limitations and scope of existing methods to know the extent of their application, more rigorous mathematical interpretation procedures, development of methods for the detection of scattered sulphides, and drill‐hole and underground exploration techniques are suggested as worthy of study.
GEOPHYSICAL DATA ON THE NORTH CAROLINA COASTAL PLAIN
Authors: Skeels D. C.
Published: October 2002

Results are given of surveys conducted in 1944–1946 by the Esso Standard Oil Company in northeastern North Carolina, and extending into the southeast corner of Virginia. Gravitational, magnetic, refraction and reflection surveys were made. The gravity and magnetic maps indicate a basement of complex composition, with a grain approximately north‐south. The refraction data show the regional eastward dip of a high velocity layer, which in the western part of the area is identified as crystalline basement, but which in the eastern part is believed to be a limestone in the Lower Cretaceous. The reflection survey of Pamlico Sound shows regional east dip with a number of noses plunging east and northeast, and some possible faults but no closed structures.
THE CASE FOR GRAVITY DATA FROM BOREHOLES
Authors: Smith Neal J.
Published: October 2002

The immediate urge for gravity meter surveys in boreholes is the desire to improve the gravity method itself but there are other potential uses for data so obtained. Borehole gravity surveys, through the influence of density, would be related to numerous important rock properties such as the velocity of seismic waves, the coefficient of reflection, the electrical resistivity, lithology, porosity, and the kinds and states of fluids in the rock. Therefore, in addition to improvement in gravity prospecting, the data would bear upon seismic techniques and, depending on accuracy and detail, upon the interpretation of lithologic and electric logs. The more obvious of the possible uses are indicated and some of the problems and inherent limitations holding up development are discussed.
DEPENDENCE OF SEISMIC WAVE VELOCITY UPON DEPTH AND LITHOLOGY
Authors: West S. S.
Published: October 2002

Interval velocity v in relatively pure clastic sediments can be expressed as a function of depth z by the formula [Formula: see text], where [Formula: see text] is a constant characteristic of the rock and [Formula: see text], approximately. From this relation can be deduced a function [Formula: see text], which prescribes the minimum velocity possible at a given depth and the maximum depth at which a given velocity can occur. An upper limit of velocity is set by data from limestones and from refraction measurements at depths from 8 to 50 km. The limiting curves converge near 150 km depth toward a function [Formula: see text], which holds from 200 km to the boundary of the core at 2900 km. The relation of near‐surface velocity to porosity is discussed, and it is shown how one can deduce the motion of shorelines during deposition.
SEISMIC VELOCITY AS A FUNCTION OF DEPTH AND GEOLOGIC TIME
Authors: Faust L. Y.
Published: October 2002

Velocity data are compiled from measurements of nearly 1,000,000 feet of section in 500 well surveys in the United States and Canada. Average velocities for shale and sandstone sections are arranged by depth and geologic age. Deviations from the mean values are attributed to lithologic variations. The variations of velocity with depth and time are studied independently in order to develop a quantitative relationship. It is concluded that the velocity for an average shale and sand section is given by the equation [Formula: see text], where V is velocity in feet per second, Z is depth in feet, and T is age in years. Velocities in limestone show less definite evidence of increase with age and depth.
CORE HOLE VELOCITY SURVEYS
Authors: Henderson J. B. H. , Brewer R.
Published: October 2002

A method for conducting velocity surveys in exploratory core holes has been developed. A gun perforator is used in connection with electric logging equipment. Below fifty feet, errors are small. Results are satisfactory in programs described in north Louisiana, south Arkansas, and North Dakota.
GHOST REFLECTIONS CAUSED BY ENERGY INITIALLY REFLECTED ABOVE THE LEVEL OF THE SHOT
Authors: Van Melle F. A. , Weatherburn K. R.
Published: October 2002

Some experiments are described which demonstrate the occurrence of an initial reflection from above shot level and of a resultant secondary reflection from depth which, by optical analogy, may be termed a ghost reflection. The reflector above shot level was in this case the base of the weathered layer. Reflection coefficients as high as [Formula: see text] were found in the Pleistocene Beaumont clay surface in Harris County, Texas. With reflection coefficients of this magnitude, the ghost reflections influence the character of seismograms noticeably.
THE REFRACTION ARRIVAL IN WATER COVERED AREAS
Authors: Officer Charles B.
Published: October 2002

A solution is given for the refraction arrival in water covered areas in terms of the evaluation of a branch line integral for an impulsive point source. The physical significance of the mathematical solution is discussed, and experimental verification of the theoretical predictions is presented. The character, frequency, and range dependence of the refraction arrival agree with theory. Using the results of this theory and the conventional interpretation techniques for refraction seismograms, it is possible to determine the velocities and depths of the seismic refraction horizons from the record of a single receiver. The velocities of the refraction layers can be determined from the frequency of the refraction arrivals, the depth of water, and the velocity of sound in water. Then, from the travel times the depths of the horizons can be computed. This method could be of importance in reconnaissance measurements of geologic structure over the continental shelves.
A FIELD EVALUATION OF THE ELECTROMAGNETIC REFLECTION METHOD
Authors: Orsinger Albert , Van Nostrand Robert
Published: October 2002

Previous publications have outlined the general theory of electromagnetic wave propagation along an interface such as the air‐earth boundary and described model experiments in which this theory was verified. Equipment similar to that described for the laboratory experiments has been adapted for field use. Two large loops, one for transmitting and the second for receiving, are laid on the surface of the ground and a current square wave is passed through the transmitting loop. A similar arrangement of loops is placed on the surface of a metallic model. The signals from the two receiving loops are mixed in opposition. The layering in the model is then manipulated until the difference signal is a minimum, which condition signifies that the actual earth has been approximated in the model, after account is taken of the appropriate scaling factors. At five stations in Dallas County, Texas, this technique was used to determine the depth of the Austin chalk‐Eagle Ford shale contact, which varies from 50 to 400 feet, within an average accuracy of about five per cent.
COMPLEX REFLECTION PATTERNS AND THEIR GEOLOGIC SOURCES
Authors: Rieber Frank
Published: October 2002

A technic is shown for producing synthetic records corresponding to assumed ideal structural conditions, the resulting records being reproduced in the usual visual form, and also in the form of directionally analyzed records. Examples of folding, faulting and irregular sedimentation are treated.
SEISMIC VELOCITIES FROM SURFACE MEASUREMENTS
Authors: Dix C. Hewitt
Published: October 2002

The purpose of this paper is to discuss field and interpretive techniques which permit, in favorable cases, the quite accurate determination of seismic interval velocities prior to drilling. A simple but accurate formula is developed for the quick calculation of interval velocities from “average velocities” determined by the known [Formula: see text] technique. To secure accuracy a careful study of multiple reflections is necessary and this is discussed. Although the principal objective in determining velocities is to allow an accurate structural interpretation to be made from seismic reflection data, an important secondary objective is to get some lithological information. This is obtained through a correlation of velocities with rock type and depth.
LINE SPACING EFFECT AND DETERMINATION OF OPTIMUM SPACING ILLUSTRATED BY MARMORA, ONTARIO MAGNETIC ANOMALY
Authors: Agocs W. B.
Published: October 2002

The airborne magnetometer data of the Marmora iron ore deposit at Marmora, Ontario have been used as an example to show the results obtained by the use of various line spacings ranging from 1 mile to 1/4 mile. The maps show how easy it is, in any type of geophysical survey, to miss a feature of economic value if the line spacing is too coarse. The probability equations are given for the crossing of randomly oriented features whose maximum dimension is less than the spacing of the control lines for circular, elongate, and rectangular outlines. The equations are [Formula: see text]; [Formula: see text]; [Formula: see text]; [Formula: see text]; [Formula: see text]; and [Formula: see text]; respectively where P is the probability; D is the diameter; L is the length; W is the width; and S and T are line spacings.
SEISMIC WAVE STUDIES OVER A HIGH‐SPEED SURFACE LAYER
Authors: Press Frank , Dobrin Milton B.
Published: October 2002

The propagation of compressional, shear, and surface waves was studied along a 3,200 ft profile at a location where a 95‐ft‐thick surface layer of Austin chalk, with a compressional velocity of about 9,900 ft/sec, overlies a 400‐ft section of Eagle Ford shale with a speed of about 6,500 ft/sec. Woodbine sand, with a velocity of about 9,900 ft/sec, underlies the shale. Refracted first arrivals transmitted through the high speed surface layer show an increase of frequency with distance from the shot. A refracted second arrival from the Woodbine decreases in frequency and, after correction for spreading, increases in relative amplitude with distance. This would indicate that the high‐speed surface layer acts as a high‐pass filter for energy transmitted horizontally and as a low‐pass filter for energy transmitted vertically through the layer. Shear waves transmitted through the Austin chalk are also observed. Surface waves consist of two groups of arrivals; a brief train of high‐frequency waves (greater than 20 cps) propagated almost entirely in the surface layer is followed by a short train of low frequency waves. Unlike surface waves in most other localities, the two groups show almost no dispersion. The characteristics of both kinds of waves are interpreted qualitatively in terms of the layering.
GEOMAGNETIC MEASUREMENTS IN THE GULF OF MEXICO AND IN THE VICINITY OF CARYN PEAK
Authors: Miller Edward Titus , Ewing Maurice
Published: October 2002

Maps of the earth’s total magnetic intensity at a 100‐gamma contour interval are presented for most of the Gulf of Mexico and about 12,600 square miles surrounding Caryn Peak in the northwestern Atlantic. These were prepared mainly from data obtained during VEMA cruise No. 3 early in 1954. The field is remarkably uniform over an area including the deep basin of the Gulf of Mexico and extending northward almost to Texas and Louisiana. Numerous essentially circular anomalies of several hundred gammas amplitude exist near the edges of the calcareous West Florida and Campeche Banks. Caryn Peak exhibits a similar anomaly which is attributed to remanent magnetization of basic igneous rock. It is concluded that at Caryn Peak during the volcanic activity, probably in late Cretaceous time, the earth’s magnetic field had approximately the same direction as now. It is concluded that the scarps bounding the calcareous banks are not tectonic. It is suggested that they roughly coincide with lines of now buried basic volcanoes around which the limestone banks developed. In the area of the Gulf of Mexico which has been surveyed there is no anomaly like the several hundred gamma linear positive found off the eastern coast of North America, near the transition from a thick continental to a thin oceanic crust. If present, it must lie near the shoreline in the vicinity of Texas and Louisiana. This supports other evidence that the crust beneath the outer shelf and continental rise off Texas and Louisiana is of a thin oceanic type similar to that under the main basin. In this interpretation a thick column of sediments has spread out over part of the deep basin.
CALCULATION OF GUARD ELECTRODE RESPONSE CURVES
Authors: De Witte Leendert , Fournier Kenneth P. , Tejada‐Flores Hernan
Published: October 2002

In the existing theories of guard electrode logging, the electrode is approximated by a prolate spheroid. All equipotential surfaces are assumed to be concentric prolate spheroids and the current nappes are bounded by hyperboloids. This picture ignores the refraction of current at the boreface and at the boundary of invaded zones of porous formations. A new approach to guard electrode theory has been formulated in which the electrode is represented by a series of spheres having the same diameter as the electrode. The boreface and invaded zone boundary are considered to be cylindrical. The current from each sphere is calculated from the condition that all spheres must be at the same potential and the potential distribution is found by superposition of the fields due to the individual currents. For small drill holes in otherwise homogeneous formations of moderate resistivity the prolate spheroid approximation gives results that are identical with those of the present theory. For larger holes, invaded formations and large resistivity contrasts, the prolate spheroid method is shown to give varying degrees of error in the calculated apparent resistivities.
PROPAGATION OF TRANSIENT ELECTROMAGNETIC WAVES IN A MEDIUM OF FINITE CONDUCTIVITY
Authors: Bhattacharyya Bimal Krishna
Published: October 2002

Transient electric and magnetic fields have been calculated for ramp function and sawtooth current sources immersed in a semi‐conducting medium. An electric dipole source has been assumed. In the case of ramp function input, it is observed that the peaks of the overshoots in the θ‐component of the electric field decrease in magnitude with the increase in rise time of the input pulse. It has also been shown that the rise time of the current pulses has definite effect upon the rise time and amplitude of the electric fields and that the sawtooth exciting pulses having large values of rise time may be conveniently used to obtain measurable values of the electric and magnetic fields.
PREDICTIVE DECOMPOSITION OF SEISMIC TRACES
Authors: Robinson Enders A.
Published: October 2002

The generalized harmonic analysis, or spectral decomposition, of a time series results in its representation in terms of its harmonic, or sinusoidal, components. This paper, on the other hand, develops in an expository manner the generalized regression analysis, or predictive decomposition, of a time series. This decomposition results in the representation of the time series at any moment in terms of its own observable past history plus an unpredictable, random‐like innovation. For the purposes of this paper, it is assumed that a seismic trace (recorded with automatic volume control) is additively composed of many overlapping seismic wavelets which arrive as time progresses. It is assumed that each wavelet has the same stable, one‐sided, minimum‐phase shape and that the arrival times and strengths of these wavelets may be represented by a time sequence of uncorrelated random variables. By applying the predictive decomposition theorem, it is shown how the wavelet shape may be extracted from the trace, leaving as a residual the strengths of the wavelets at their respective arrival times.
PHYSICAL ANALYSIS OF DEEP SEA SEDIMENTS
Authors: Sutton George H. , Berckhemer Hans , Nafe John E.
Published: October 2002

A sonic pulse system, similar to that used at Lamont Geological Observatory for seismic model experiments, was used aboard the Research Vessel VEMA during the summer of 1954 to determine high frequency seismic velocities in fresh deep sea sediment cores. Velocity profiles were obtained from 26 cores covering a wide range of lithologies and ages (Recent to Miocene). Density, porosity, median grain size, sorting, carbonate content, and salt content were also measured. The compressional wave velocity in the ocean‐bottom unconsolidated sediments studied is well represented by the equation: [Formula: see text] where v′=compressional wave velocity in km/sec ϕ=median grain size in phi units γ=percentage of HCl soluble material η=porosity. Many measurements gave velocities less than the velocity of sound in sea water. Most of the low carbonate samples followed a velocity‐porosity relation given by the Wood (1941) equation. The regression coefficient, −.44η, agrees well with the average slope of the Wood equation over the observed porosity range. High carbonate and large median grain size samples gave velocities above that predicted by the Wood equation. These higher velocities are explained as the combined result of shear strength and low effective porosity in the samples. The highest velocities were found in slowly deposited sediments. The degrees of sorting of the sediments had no observable effect on the seismic velocities except that unexplained variations were greater for more poorly sorted materials. No correlation between velocity and age was evident in the sediments studied. The effect of temperature, between 40 and 80°F. on compressional velocity in sediments may be explained by changes in elastic properties of the water fraction alone. The effect of compaction in the upper 15 or 20 feet of homogeneous sediments produced a change in seismic velocity not greater than 1 or 2 percent. Attenuation was greater in the coarse‐grained high‐velocity sediments than in sediments of smaller grain size.
THE ABSORPTION OF SOUND IN SEDIMENTS
Authors: Busby J. , Richardson E. G.
Published: October 2002

Measurements were made of the attenuation of sound in compacted sediments in water using an ultrasonic wave train at frequencies in the megacycle range. Artificial sediments of glass spheres as well as marine sands have been tested and the variation of absorption with frequency, mean grain size, and concentration are illustrated.
POTENTIAL DISTRIBUTION DUE TO A CYLINDRICAL ELECTRODE MOUNTED ON AN INSULATING PROBE
Authors: de Witte Leendert , Gould Roy W.
Published: October 2002

The potentials around a finite cylindrical electrode can be obtained by dividing the electrodes into rings of equal thickness and substituting an infinitely thin current ring for each of the slices. The field of an infinitely thin ring electrode mounted on an insulating cylindrical probe of the same diameter can be found by combining the properties of the delta function with a solution of Laplace’s equation in cylindrical co‐ordinates. Combination of solutions for the infinitely thin rings under the condition that the potential of the electrode surface be constant leads to a system of simultaneous linear equations. By increasing the number of slices, the potential around the finite electrode can be found arbitrarily close. The problem of a cylindrical electrode on a sonde located coaxially in a conducting hole, drilled through a medium of different conductivity, is treated by the same method. This arrangement is of interest in electrical logging of drill holes. Numerical examples have been calculated on an IBM 650 magnetic drum computer. The potential along the surface of the insulating probe, at distances larger than twice the electrode length, can be approximated with good accuracy by assuming that all of the current is emitted from an infinitely thin ring located in the median plane of the electrode.
SUB‐BOTTOM DEPTH RECORDER
Authors: Beckmann Walter C. , Roberts Archie C. , Luskin Bernard
Published: October 2002

The Sub‐bottom Depth Recorder (SDR) has been developed to study the underlying geologic structure of water covered areas. The SDR is essentially a broad‐band, high‐powered echo sounder which utilizes one of two sound sources. The first, an electrical spark discharge (Sparker), has produced penetrations in excess of 600 ft in 50 ft of water. The second, a combustion chamber using a mixture of propane and oxygen (RASS), has produced penetrations in excess of 1,400 ft in 80 ft of water. Results obtained from the SDR have been found to be in excellent agreement with test boring and seismic refraction data.
THE ELECTROCHEMICAL MECHANISM OF SULFIDE SELF‐POTENTIALS
Authors: Sato Motoaki , Mooney Harold M.
Published: October 2002

Self‐potentials associated with a sulfide ore body result from the ohmic potential drop within the country rocks. The electric current is produced by separate but simultaneous reduction of oxidizing agents near the surface and oxidation of reducing agents at depth. The ore does not participate directly in either reaction, but serves as a conductor to transfer the electrons from the reducing agents to the oxidizing agents. The possibility for the above reactions to occur depends upon differences in oxidation potential of ground waters at different depths. In the zone of weathering, the oxidation potential is controlled by the reduction mechanism of oxygen, and ranges in value from 0.2 to 0.7 volt (on the hydrogen scale). If the ore tends to oxidize at some lower potential, then the latter is the available one. In the zone beneath the water table, the potential is probably controlled by the oxidation‐reduction equilibria of iron‐rich minerals, and ranges in value from 0 to −0.3 volt. The available potential is independent of ore type. The maximum potential difference available to produce natural currents is estimated at: graphite 0.8, pyrite 0.7, covellite 0.6, chalcocite 0.5, galena 0.3 volt. Self‐potentials will be large if the ore body (1) is composed of minerals difficult to oxidize, (2) has low electrical resistance (physical continuity together with low resistivity), (3) extends vertically across the water table, and (4) exists close to the surface.
DENSITY LOGGING
Authors: Pickell J. J. , Heacock J. G.
Published: October 2002

This review of density logging is primarily a compilation of information presented in the petroleum industry literature. It includes a brief discussion of some of the theory involved in gamma‐ray density logging, various calibration curves, comparisons of density‐log and core data, and comments on density‐log interpretation. Conclusions are that the density log, under good borehole conditions, provides an accurate means for measuring bulk density of the formation adjacent to the borehole. If grain density is known, valid estimates of porosity can also be made. Because of the response characteristics of the system, accuracy in determining porosity is best when formation densities are low and porosities are high.
THE APPLICATION OF VARIOUS GEOPHYSICAL TECHNIQUES TO SPECIALIZED ENGINEERING PROJECTS
Authors: McGuinness William T. , Beckmann Walter C. , Officer Charles B.
Published: October 2002

Sonic and seismic methods applied to marine and land civil engineering projects and several unique techniques applied to specialized problems encountered in engineering are described. The geophysical techniques discussed include Sparker and Gas Exploder surveys for marine site investigations, measurements of ground motion for quiet instrument facilities, undersea cable environmental studies, and in situ determination of pile lengths.
VARIATION OF ELECTRICAL RESISTIVITY OF RIVER SANDS, CALCITE, AND QUARTZ POWDERS WITH WATER CONTENT
Authors: Sarma V. V. Jagannadha , Rao V. Bhaskara
Published: October 2002

Electrical resistivity variations of samples of graded river sands, calcite, and quartz powders are studied for different moisture contents of varying salinities. The variations exhibit a general hyperbolic trend. For the same grain size, the critical saturation index of a sample is constant and independent of the salinity of moisture content. The smaller the grain size, the larger the saturation index. The critical saturation index of a sample is correlated with its retentive capacity, and it is shown, from studies of the quartz samples, that, for grain sizes of the order of clay particles, the critical moisture would reach 100 percent.
THE GRAVIMETER IN STUDIES OF BURIED VALLEYS
Authors: Hall D. H. , Hajnal Z.
Published: October 2002

In glaciated areas, variation in density and thickness of the drift or of members within it is often an important cause of gravity anomalies. This can be utilized whenever the drift is the principal object of attention, such as in prospecting for ground water. Trends of gravity lows near Kindersley, Saskatchewan, some with amplitude of one milligal, appear to be connected with buried valleys formerly occupied by the South Saskatchewan River and its tributaries. Calculation from detailed gravimeter traverses and comparison with borehole samples give estimates of the thickness and density contrasts of the fill in the valleys. These indicate a low‐density sand section with a thickness of up to 250 ft and a density contrast of 0.27 gm/cc for the buried valley of the South Saskatchewan River; and a low‐density silt section with a thickness of up to 400 ft and a density contrast of 0.25–0.35 gm/cc for a buried tributary valley. Density measurements indicate that contrasts within the drift can be as large as those between bedrock and drift. It is thus possible to detect buried valleys which have been cut entirely into drift, as well as those cut into bedrock.
REPLY BY AUTHORS TO DISCUSSION BY W. T. HIGDON
Authors: Sarma V. V. Jagannadha , Rao V. Bhaskara
Published: October 2002

The introductory statement that “The electrical resistivity of a geological formation is a function of … (1) the amount of moisture and consequently of porosity; (2) salinity of the moisture; and (3) grain size of the formation” is intended as a broad generalization to include possible parameters affecting resistivity variations. Of these three parameters, only the influence of the amount of moisture on the electrical resistivity variations is the subject of the results reported. At the same time, the possible effects of the other two parameters have been taken into consideration in the control of experiments and discussion of results. Thus, at least three samples (2, 3, and 4) of known average grain sizes of 1.5, 0.75, and 0.37 mm are treated with five samples of water with a wide range of known salinities. By such a distribution, it is ensured that the electrical resistivity variations of the sample in a given run are due only to the varying water content. Corrections to the data required for representation are thus avoided.
ELECTROMAGNETIC FIELDS OF A VERTICAL MAGNETIC DIPOLE PLACED ABOVE THE EARTH’S SURFACE
Authors: Bhattacharyya B. K.
Published: October 2002

Electromagnetic fields due to a small loop antenna placed above the surface of a homogeneous and isotropic earth have been calculated. The effect of both the conduction and displacement currents are taken into account. Because of the complexity of the functions defining the fields, expressions valid separately for high and low frequencies are developed for the electric and magnetic field components. These expressions are then utilized to determine, for a step‐function current source, (a) the mutual impedance function [Formula: see text] between the primary loop and a small length of wire and (b) the voltage v(t) induced in a secondary loop. Two parameters are used to fix the locations of the primary loop and the receiving antenna with respect to the earth. A number of curves are plotted showing the mutual impedance function and the voltage function against time for different values of the parameters and the conductivity and the permittivity of the earth. With increase in either the conductivity or the permittivity, the amplitude and the rate of decay of the two functions decrease appreciably. However, the amplitudes of both [Formula: see text] and v(t) become smaller and the rate of decay higher as the receiving antenna is gradually lifted vertically from the ground. For all values of permittivity, the amplitude of the mutual impedance rises to a maximum with the horizontal separation between the two antennas before beginning to decrease, but at the same time the rate of decay of the transient becomes faster. With increase in the horizontal separation, the amplitude of the voltage function decreases inversely as the fifth power of the distance between the image of the transmitting dipole and the receiving antenna, but the rate of decay increases markedly.
A DISCUSSION OF THE “FAULT” AND “DIKE” PROBLEMS IN MAGNETOTELLURIC THEORY
Authors: Weaver J. T.
Published: October 2002

In two recent papers appearing in Geophysics, d’Erceville and Kunetz (1962) and Rankin (1962) have dealt with the magnetotelluric theory for a plane earth which contains a certain type of vertical fault. In both cases the results depend on a boundary condition which requires the assumption that the normal component of current density vanishes at the surface of the earth. While d’Erceville and Kunetz confine their attention to the region below the surface and thereby avoid explicit mention of the source field, Rankin follows Cagniard (1953) by considering a plane‐polarized electromagnetic wave normally incident on the surface of the earth. In this case, the assumed boundary condition is not correct, as we shall see later; indeed, it actually leads to a contradiction.
ANALYSIS OF VARIABLE‐DENSITY SEISMOGRAMS BY MEANS OF OPTICAL DIFFRACTION
Authors: Jackson Philip L.
Published: October 2002

Variable‐density seismograms were originally developed in exploration work to aid in the visualization of strata formations. They can also be directly analyzed by means of optical diffraction. When a plane wave of spatially coherent monochromatic light passes through a variable‐density seismogram, a diffraction pattern can be formed which defines the seismic frequencies. The seismogram is placed so that it affects the incident light in the same manner as a diffraction grating in a conventional spectroscopic apparatus. Resulting diffraction patterns reveal continuous energy‐density spectra over a range of about nine octaves. The spectra are normally two‐dimensional. When variable‐density profiles are used, the second dimension of the spectra is wavenumber, which is expressed as the diffraction caused by density variations across the data channels. The spectra can be made one‐dimensional by inserting a cylindrical lens so that an image of the seismograms is formed in one direction in the same plane that Fraunhofer diffraction occurs in a perpendicular direction. By this means multichannel spectral analysis is performed. An additional lens is used to image the seismogram after the light has passed through the diffraction plane. The image can be filtered as to frequency, wavenumber, or propagation velocity when suitable obstructions are placed in the diffraction plane. By properly combining optical diffraction and imaging, one can obtain or perform the following: energy‐density spectra, time‐varying spectra, constant apparent wavenumber spectra, dispersion measurements, apparent velocity of narrow‐band energy, frequency filtering, wavenumber filtering, wideband velocity filtering, and correlations.
TWO‐DIMENSIONAL FILTERING AND THE SECOND DERIVATIVE METHOD
Authors: Meskó C. A.
Published: October 2002

The data‐processing operations of second derivative formulas are equivalent to two‐dimensional digital filtering operations. Therefore any coefficient set can be described unambiguously by its two‐dimensional frequency response. The frequency responses can be represented by surfaces over the two‐dimensional frequency plane. We have simplified the representation by giving some curves intersected from these surfaces by a) planes, b) cylindrical surfaces perpendicular to the frequency plane. The coefficient sets given by Elkins (1951), Henderson and Zietz (1949), Rosenbach (1953), and the “center‐point‐and‐one‐ring” method are analysed. These formulas, in order of increasing “average” accuracy of approximation, are Henderson and Zietz, Rosenbach, “center‐point‐and‐one‐ring” method, Elkins. Henderson and Zietz’s formula and the “center‐point‐and‐one‐ring” method have depended significantly on direction, while Rosenbach’s formula is nearly nondirectional. Elkins’ formula lies between them.
THE DEVELOPMENT AND USE OF A HIGH‐PRECISION DOWNHOLE GRAVITY METER
Authors: Howell Lynn G. , Heintz K. O. , Barry A.
Published: October 2002

The vibrating string downhole gravity meter described has a precision of about .01 mgal in gravity measurement. With measurements of this precision, density of a 30‐ft section in the subsurface can be determined with an accuracy of [Formula: see text]. These density measurements are useful in gravity interpretation, in computing acoustic impedance for use in seismology, and in estimating porosities of formations. Examples of density profiles measured in boreholes are given.
ESTIMATION OF THE DIRECTION OF MAGNETIZATION OF A BODY CAUSING A MAGNETIC ANOMALY USING A PSEUDO‐GRAVITY TRANSFORMATION
Authors: Bott M. H. P. , Smith R. A. , Stacey R. A.
Published: October 2002

A two‐dimensional form of the pseudo‐gravity transformation, applicable to bodies magnetized in directions not parallel to the ambient field, is given. Assuming that a body of finite cross section is magnetized in the same direction and sense at every point, then an adaptation of this pseudo‐gravity transformation enables the direction of magnetization of the body to be estimated, within limits, from the magnetic anomaly it causes. The method has been programmed for a computer. A simple extension enables it to be applied to three‐dimensional bodies. The method is shown to be reliable by testing it against calculated magnetic profiles over geometrical shapes. It is applied to the Lambay magnetic anomaly in the west Irish Sea, showing this to be caused by a body magnetized approximately in the direction of the present earth’s field.
PREFERENTIAL EXCITATION OF REFRACTING INTERFACES BY USE OF A SOURCE ARRAY
Authors: Laster Stanley J. , Linville A. Frank
Published: October 2002

Normally, the method of isolating the critically refracted energy from a single interface has been the design of shot to recorder distance to make a particular refraction the first arrival. Later energy, associated with the same interface and from other interfaces, plus scattered energy produces a complex interference pattern following the first arrival which often can not be interpreted. However, the received data may be processed by array techniques to separate these interfering events. The technique presented here involves the use of a source array, each element in the array being separately recorded and digitally combined to provide, in turn, preferential excitation of each of the refracting interfaces of interest. Field recordings for a single source‐receiver geometry have been processed to separate the interfering energy from two refracting interfaces to the extent that the secondary event may be used for mapping. Array processing also facilitates the study of late arriving scattered events.
THE EFFECT OF STRESS RATE AND TEMPERATURE ON THE STRENGTH OF BASALT AND GRANITE
Authors: Kumar A.
Published: October 2002

The ultimate strengths of basalt and granite were measured over a range of stress rates from 2×10 to [Formula: see text] psi per second. A comparison of basalt and granite showed that, although their static strengths were close, their dynamic strengths were different. The static strengths of basalt and granite were 27.5 and 29 kpsi, respectively, at the stress rate of 2×10 psi per second while their strengths at the stress rate of [Formula: see text] psi per second were 59 and 70 kpsi, respectively. In order to obtain an insight into the basic mechanisms of rock fracturing, the combined effects of stress rate and temperature were studied. The strength of basalt was increased from 27.5 kpsi at room temperature to 45 kpsi at liquid nitrogen temperature at the stress rate of 2×10 psi per second. The mechanisms of fracturing were thermally activated. The activation energy for basalt at 50 kpsi equalled 450 calories per mole. The dynamic modulus of basalt measured by the pulse technique was [Formula: see text] psi. The value of the dynamic modulus obtained at a stress rate of [Formula: see text] psi per second was [Formula: see text] psi.
ELECTRIC POTENTIAL NEAR A SPHERICAL BODY IN A CONDUCTING HALF‐SPACE
Authors: Large David B.
Published: October 2002

An extensive summary of classical potential solutions has been given recently by Van Nostrand and Cook (1966). This note presents a solution for the potential due to a point source of electric current placed on the earth’s surface in the vicinity of a buried spherical body of arbitrary resistivity. The analysis follows the procedure suggested by Van Nostrand and Cook and is similar to that used recently by Merkel (1969, 1971).
SOME STUDIES RELATING TO NONUNIQUENESS IN GRAVITY AND MAGNETIC INVERSE PROBLEMS
Authors: Al‐Chalabi Mahboub
Published: October 2002

Polygonal models which are of uniform density or magnetization contrast and which contain no cavities are sufficient to ensure the uniqueness of solutions in gravity and magnetic problems. Nonuniqueness is then attributed to a number of other factors which are discussed in detail. We study the problem of nonuniqueness using mainly a parameter hyperspace in which ambiguity takes the form of a scatter of local minima or a continuous domain bounded by a contour whose value is determined by the amplitude of observational errors. The possible solutions to the problem being examined are contained in a region which would have contained the unique solution under exact conditions and which decreases in extent as the factors causing ambiguity decrease. Thus, under favorable conditions, a large degree of uniqueness may occur. By starting the search from a good initial point based on all available information, we may obtain a satisfactory solution without specifying any of the parameters defining the model. Different solutions produced by different initial points vary in their emphases but are, generally, of the correct order of magnitude. When such favorable conditions are lacking, the extent of ambiguity may be reduced by specifying one or more parameters. With the aid of the parameter hyperspace, we may thus conceive why and how ambiguity is present and determine what means can be found to limit it.
HYDROGEOLOGIC AND ENGINEERING‐GEOLOGIC POSSIBILITIES FOR EMPLOYING THE METHOD OF INDUCED POTENTIALS
Authors: Ogilvy A. A. , Kuzmina E. N.
Published: October 2002

The method of induced potentials is applied in groundwater and certain types of engineering‐geologic investigations. Because of the complex nature of induced polarization in ion‐conducting media, the subject still has not been sufficiently studied. This phenomenon is evidently associated with the diffusion processes occurring between narrow and wide capillaries and affected by membrane potentials in the presence of clay fractions. The laboratory experiments have proved the dependence of induced potentials of sandy‐clayey media on their particle‐size distribution pattern, porosity, moisture content, interporous moisture, salinity degree, and temperature. Modeling accomplished with horizontally layered sections and lenses of fresh and saline waters has given data for analyzing polarizability behavior in heterogeneous media. Field investigations have been carried out in Central Kazakhstan, the Crimea, Mordovia, Armenia, and the Moscow area. The data obtained testify to the applicability of this method for determining the depth to groundwaters in sandy‐clayey deposits, detecting accumulations of fresh groundwaters, and specifying the position of the interfaces between fresh and saline waters. No less important is the possible utilization of a parameter for identifying rock types and characterizing the sandy‐clayey deposits. Using field examples, the authors consider the expediency of applying the IP method for investigating massive rocks and for prospecting for water in fractured and karst rocks. The IP method significantly supplements the information obtained by conventional methods and is employed in combination with them in borehole logging. In perspective, polarizability can be used as a parameter for establishing the correlative relations between geophysical, hydrological, and strength parameters of rocks.
TIME‐DEPENDENT ELECTROMAGNETIC FIELDS OF AN INFINITE, CONDUCTING CYLINDER EXCITED BY A LONG CURRENT‐CARRYING CABLE
Authors: Verma Saurabh K.
Published: October 2002

Theoretical and numerical computations have been made for the quasi‐static, time‐domain electromagnetic response of an infinite, conducting horizontal cylinder stimulated by long cable‐carrying step and ramp‐function type pulses. The effect of higher‐order induced multipoles on the secondary electric and magnetic field components is analyzed in detail, and the “threshold distances” at which individual multipoles become effective (contributing more than 5 percent of the secondary field) are presented. Also, the field fall‐off directly above the body and the variations in different induced‐field components along a traverse perpendicular to the strike of the ore body are examined.
HOW THIN IS A THIN BED?
Authors: Widess M. B.
Published: October 2002

Based on reflective properties, a thin bed may be conveniently defined as one whose thickness is less than about [Formula: see text] where [Formula: see text] is the (predominant) wavelength computed using the velocity of the bed. The amplitude of a reflection from a thin bed is to the first order of approximation equal to [Formula: see text] where b is the thickness of the bed and A is the amplitude of the reflection if the bed were to be very thick. The equation shows that a bed as thin as 10 ft has, for typical frequency and velocity, considerably more reflective power than is usually attributed to it.