bluuebunny/crossref_metadata_2025 huggingface dataset:
Decreased susceptibility of leukemic cells with PIG-Amutation to natural killer cells in vitro
Authors: Nagakura Shoichi , Ishihara Sonoko , Dunn Daniel E. , Nishimura Jun-ichi , Kawaguchi Tatsuya , Horikawa Kentaro , Hidaka Michihiro , Kagimoto Tadashi , Eto Nozomu , Mitsuya Hiroaki , Kinoshita Taroh , Young Neal S. , Nakakuma Hideki
Published: October 2002

The cloning of the PIG-A gene has facilitated the unraveling of the complex pathophysiology of paroxysmal nocturnal hemoglobinuria (PNH). Of current major concern is the mechanism by which a PNH clone expands. Many reports have suggested that an immune mechanism operates to cause bone marrow failure in some patients with PNH, aplastic anemia, and myelodysplastic syndromes. Because blood cells of PNH phenotype are often found in patients with these marrow diseases, one hypothesis is that the PNH clone escapes immune attack, producing a survival advantage by immunoselection. To test this hypothesis, we examined the sensitivity of blood cells, with or withoutPIG-A mutations, to killing by natural killer (NK) cells, using 51Cr-release assay in vitro. To both peripheral blood and cultured NK cells, PIG-A mutant cells prepared from myeloid and lymphoid leukemic cell lines were less susceptible than their control counterparts (reverted from the mutant cells by transfection with a PIG-A cDNA). NK activity was completely abolished with concanamycin A and by calcium chelation, indicating that killing was perforin-dependent. There were no differences in major histocompatibility (MHC) class I expression or sensitivity to either purified perforin or to interleukin-2–activated NK cells betweenPIG-A mutant and control cells. From these results, we infer that PIG-A mutant cells lack molecules needed for NK activation or to trigger perforin-mediated killing. Our experiments suggest that PIG-A mutations confer a relative survival advantage to a PNH clone, contributing to selective expansion of these cells in the setting of marrow injury by cytotoxic lymphocytes.
Nucleotides induce chemotaxis and actin polymerization in immature but not mature human dendritic cells via activation of pertussis toxin–sensitive P2y receptors
Authors: Idzko Marco , Dichmann Stefan , Ferrari Davide , Di Virgilio Francesco , la Sala Andrea , Girolomoni Giampiero , Panther Elisabeth , Norgauer Johannes
Published: October 2002

Dendritic cells (DCs) are considered the principal initiators of immune response because of their ability to migrate into peripheral tissues and lymphoid organs, process antigens, and activate naive T cells. There is evidence that extracellular nucleotides regulate certain functions of DCs via G-protein–coupled P2Y receptors (P2YR) and ion-channel–gated P2X receptors (P2XR). Here we investigated the chemotactic activity and analyzed the migration-associated intracellular signaling events such as actin reorganization and Ca++ transients induced by common P2R agonists such as adenosine 5′-triphosphate (ATP) and 2-methylthioadenosine triphosphate, the P2YR agonists UTP and adenosine 5′-diphosphate (ADP), or the P2XR agonists αβ-methylenadenosine-5′-triphosphate and 2′,3′-(4-benzoyl)benzoyl-ATP. The common P2R agonists and the selective P2YR agonists turned out to be potent chemotactic stimuli for immature DCs, but not for mature DCs. In contrast, P2XR agonists had only marginal chemotactic activity in both DC types. Chemotaxis was paralleled by a rise in the intracellular Ca++concentration and by actin polymerization. Studies with pertussis toxin implicated that intracellular signaling events such as actin polymerization, mobilization of intracellular Ca++, and migration induced by nucleotides was mediated via Gi/oprotein–coupled P2YR. Moreover, functional studies revealed selective down-regulation of this Gi/oprotein–coupled chemotactic P2YR responsiveness during maturation, although immature and mature DCs expressed similar amounts of mRNA for the P2R subtypes (P2Y2R, P2Y4R, P2Y5R, P2Y7R, P2Y11R and P2X1R, P2X4R, P2X7R), and no major differences in respect to the mRNA expression of these receptors could be observed by semiquantitative reverse transcription and polymerase chain reaction (RT-PCR). In summary, our data describe a differential chemotactic response of immature and mature DCs to nucleotides, and lend further support to the hypothesis that P2R are a novel class of immunomodulatory plasma membrane receptors suitable for pharmacological intervention.
Interactions of STAT5b-RARα, a novel acute promyelocytic leukemia fusion protein, with retinoic acid receptor and STAT3 signaling pathways
Authors: Dong Shuo , Tweardy David J.
Published: October 2002

Signal transducer and activator of transcription (STAT) 5b-retinoic acid receptor (RAR) α is the fifth fusion protein identified in acute promyelocytic leukemia (APL). Initially described in a patient with all-trans retinoic acid (ATRA)–unresponsive disease, STAT5b-RARα resulted from an interstitial deletion on chromosome 17. To determine the molecular mechanisms of myeloid leukemogenesis and maturation arrest in STAT5b-RARα+ APL and its unresponsiveness to ATRA, we examined the effect of STAT5b-RARα on the activity of myeloid transcription factors including RARα/retinoid X receptor (RXR) α, STAT3, and STAT5 as well as its molecular interactions with the nuclear receptor corepressor, SMRT, and nuclear receptor coactivator, TRAM-1. STAT5b-RARα bound to retinoic acid response elements (RAREs) both as a homodimer and as a heterodimer with RXRα and inhibited wild-type RARα/RXRα transactivation. Although STAT5b-RARα had no effect on ligand-induced STAT5b activation, it enhanced interleukin 6–induced STAT3-dependent reporter activity, an effect shared by other APL fusion proteins including promyelocytic leukemia-RARα and promyelocytic leukemia zinc finger (PLZF)–RARα. SMRT was released from STAT5b-RARα/SMRT complexes by ATRA at 10−6 M, whereas TRAM-1 became associated with STAT5b-RARα at 10−7 M. The coiled-coil domain of STAT5b was required for formation of STAT5b-RARα homodimers, for the inhibition of RARα/RXRα transcriptional activity, and for stability of the STAT5b-RARα/SMRT complex. Thus, STAT5b-RARα contributes to myeloid maturation arrest by binding to RARE as either a homodimer or as a heterodimer with RXRα resulting in the recruitment of SMRT and inhibition of RARα/RXRα transcriptional activity. In addition, STAT5b-RARα and other APL fusion proteins may contribute to leukemogenesis by interaction with the STAT3 oncogene pathway.
Regulation of endothelial cell branching morphogenesis by endogenous chemokine stromal-derived factor-1
Authors: Salvucci Ombretta , Yao Lei , Villalba Sabrina , Sajewicz Agatha , Pittaluga Stefania , Tosato Giovanna
Published: October 2002

The chemokine stromal-derived factor-1 (SDF-1) and its unique receptor, CXCR4, are required for normal cardiovascular development, but a critical role for SDF-1 in postnatal vascular remodeling and the mechanisms underlying SDF-1/CXCR-4 vasculogenesis are unclear. Here we show that SDF-1 is expressed by the vascular endothelium from selected healthy and tumor tissues. In vitro, primary endothelial cells constitutively express SDF-1 that is detected in the cytoplasm, on the cell surface, and in the culture supernatant. Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) increase SDF-1 expression in endothelial cells. In functional studies, pertussis toxin and antibodies to SDF-1 or CXCR-4 disrupt extracellular matrix-dependent endothelial cell tube formation in vitro. This morphogenic process is associated with time-dependent modulation of surface CXCR-4 expression that changes from being diffuse to being polarized and subsequently lost. In vivo, pertussis toxin and neutralizing antibodies directed at SDF-1 inhibit growth factor–dependent neovascularization. These results indicate that SDF-1/CXCR-4 identifies VEGF- and bFGF-regulated autocrine signaling systems that are essential regulators of endothelial cell morphogenesis and angiogenesis.
Hematopoietic cells expressing the peripheral cannabinoid receptor migrate in response to the endocannabinoid 2-arachidonoylglycerol
Authors: Alberich Jordà Meritxell , Verbakel Sandra E. , Valk Peter J. M. , Vankan-Berkhoudt Yolanda V. , Maccarrone Mauro , Finazzi-Agrò Allessandro , Löwenberg Bob , Delwel Ruud
Published: October 2002

Cb2 is a novel protooncogene encoding the peripheral cannabinoid receptor. Previous studies demonstrated that 2 distinct noncoding first exons exist: exon-1A and exon-1B, which both splice to protein-coding exon-2. We demonstrate that in retrovirally induced murine myeloid leukemia cells with proviral insertion inCb2, exon-1B/exon-2 Cb2 messenger RNA levels have been increased, resulting in high receptor numbers. In myeloid leukemia cells without virus insertion in this locus, low levels of only exon-1A/exon-2 Cb2 transcripts were present and receptors could not be detected. To elucidate the function of Cb2 in myeloid leukemia cells, a set of in vitro experiments was carried out using 32D/G-CSF-R (granulocyte colony-stimulating factor receptor) cells transfected with exon-1B/exon-2 Cb2 complementary DNA and a myeloid cell line carrying a virus insertion in Cb2(ie, NFS 78). We demonstrate that a major function of the Cb2 receptor is stimulation of migration as determined in a transwell assay. Exposure of Cb2-expressing cells to different cannabinoids showed that the true ligand for Cb2 is 2-arachidonoylglycerol (2-AG), which may act as chemoatractant and as a chemokinetic agent. Furthermore, we observed a significant synergistic activity between 2-AG and interleukin-3 or G-CSF, suggesting cross-talk between the different receptor systems. Radioactive-ligand binding studies revealed significant numbers of Cb2 receptors in normal spleen. Transwell experiments carried out with normal mouse spleen cells showed 2-AG–induced migration of B220-, CD19-, immunoglobulin M–, and immunoglobulin D–expressing B lymphocytes. Our study demonstrates that a major function of Cb2 receptor expressed on myeloid leukemia cells or normal splenocytes is stimulation of migration.
Role of protein kinase C in the phosphorylation of CD33 (Siglec-3) and its effect on lectin activity
Authors: Grobe Kay , Powell Leland D.
Published: October 2002

CD33 (Siglec-3) is a marker of myeloid progenitor cells, mature myeloid cells, and most myeloid leukemias. Although its biologic role remains unknown, it has been demonstrated to function as a sialic acid–specific lectin and a cell adhesion molecule. Many of the Siglecs (including CD33) have been reported to be tyrosine phosphorylated in the cytosolic tails under specific stimulation conditions. Here we report that CD33 is also a serine/threonine phosphoprotein, containing at least 2 sites of serine phosphorylation in its cytoplasmic domain, catalyzed by protein kinase C (PKC). Phosphorylation could be augmented by exposure to the protein kinase–activating cytokines interleukin 3, erythropoietin, or granulocyte-macrophage colony-stimulating factor, in a cytokine-dependent cell line, TF-1. The CD33 cytoplasmic tail was phosphorylated by PKC in vitro, in a Ca++/lipid-dependent manner. CHOK1 cells stably expressing CD33 with cytoplasmic tails of various length also showed phorbol myristate acetate (PMA)-dependent phosphorylation of CD33. Inhibition of CD33 phosphorylation with pharmacologic agents resulted in an increase of sialic acid–dependent rosette formation. Furthermore, the occupancy of the lectin site affected its basal level of phosphorylation. Rosette formation by COS cells expressing a form of CD33 lacking its cytoplasmic domain was not affected by these same agents. These data indicate that CD33 is a phosphoprotein, that its phosphorylation may be controlled by PKC downstream of cytokine stimulation, and that its phosphorylation is cross-regulated with its lectin activity. Notably, although this is the first example of serine/threonine phosphorylation in the subfamily of CD33-like Siglecs, some of the other members also have putative target sites in their cytoplasmic tails.
A functional role of Stat3 in in vivo megakaryopoiesis
Authors: Kirito Keita , Osawa Masatake , Morita Haruhiko , Shimizu Ritsuko , Yamamoto Masayuki , Oda Atsushi , Fujita Hiroyoshi , Tanaka Masaru , Nakajima Koichi , Miura Yasusada , Ozawa Keiya , Komatsu Norio
Published: October 2002

The signal transducer and activator of transcription 3 (Stat3), a member of the Stat family of proteins, is commonly activated by thrombopoietic cytokines including thrombopoietin (TPO), interleukin (IL)-6, and interleukin-11. This finding strongly suggested that Stat3 has an important role in megakaryopoiesis and thrombopoiesis. To clarify the functional role of Stat3 in in vivo megakaryopoiesis and thrombopoiesis, we generated transgenic mice overexpressing a dominant-negative Stat3, Stat3F, to suppress the function of endogenous Stat3. To accomplish the selective expression of Stat3F in megakaryocytic lineage cells, we used the regulatory gene region of GATA-1 transcription factor selectively expressed in megakaryocytic and erythroid lineage cells. Two independent transgenic (Tg) mice lines were established. It was confirmed by Western blotting analysis that Stat3F proteins were highly expressed in the platelets from the Tg mice. In addition, it was found that Stat3 activation induced by TPO stimulation was drastically suppressed in these Tg mice compared with littermates. These findings indicate that Stat3F works well in the Tg mice. Platelet counts were within the normal range in steady-state conditions and were recovered normally from transient thrombocytopenia induced by antiplatelet serum injection. Interestingly, the platelet recovery from myelosuppression after 5-fluorouracil treatment was significantly delayed in the Tg mice. Collectively, our results strongly suggest that Stat3 plays an important role in the early stage of megakaryopoiesis, presumably through the expansion of megakaryocytic progenitor cells.
Type I interferons produced by dendritic cells promote their phenotypic and functional activation
Authors: Montoya Maria , Schiavoni Giovanna , Mattei Fabrizio , Gresser Ion , Belardelli Filippo , Borrow Persephone , Tough David F.
Published: October 2002

Resting dendritic cells (DCs) are resident in most tissues and can be activated by environmental stimuli to mature into potent antigen-presenting cells. One important stimulus for DC activation is infection; DCs can be triggered through receptors that recognize microbial components directly or by contact with infection-induced cytokines. We show here that murine DCs undergo phenotypic maturation upon exposure to type I interferons (type I IFNs) in vivo or in vitro. Moreover, DCs either derived from bone marrow cells in vitro or isolated from the spleens of normal animals express IFN-α and IFN-β, suggesting that type I IFNs can act in an autocrine manner to activate DCs. Consistent with this idea, the ability to respond to type I IFN was required for the generation of fully activated DCs from bone marrow precursors, as DCs derived from the bone marrow of mice lacking a functional receptor for type I IFN had reduced expression of costimulatory and adhesion molecules and a diminished ability to stimulate naive T-cell proliferation compared with DCs derived from control bone marrow. Furthermore, the addition of neutralizing anti–IFN-α/β antibody to purified splenic DCs in vitro partially blocked the “spontaneous” activation of these cells, inhibiting the up-regulation of costimulatory molecules, secretion of IFN-γ, and T-cell stimulatory activity. These results show that DCs both secrete and respond to type I IFN, identifying type I interferons as autocrine DC activators.
Ectopic overexpression of second mitochondria-derived activator of caspases (Smac/DIABLO) or cotreatment with N-terminus of Smac/DIABLO peptide potentiates epothilone B derivative–(BMS 247550) and Apo-2L/TRAIL–induced apoptosis
Authors: Guo Fei , Nimmanapalli Ramadevi , Paranawithana Shanthi , Wittman Sylvie , Griffin David , Bali Purva , O'Bryan Erica , Fumero Carlos , Wang Hong Gang , Bhalla Kapil
Published: October 2002

Second mitochondria-derived activator of caspases (Smac)/DIABLO is a mitochondrial protein that is released into the cytosol along with cytochrome c (cyt c) during the execution of the intrinsic pathway of apoptosis. Smac/DIABLO promotes apoptosis by neutralizing the inhibitory effect of the inhibitor of apoptosis (IAP) family of proteins on the processing and activities of the effector caspases. Present studies demonstrate that, upon engagement of the mitochondrial pathway of apoptosis, epothilone (Epo) B derivative BMS 247550, a novel nontaxane antimicrotubule agent, as well as the death ligand Apo-2L/TRAIL (tumor necrosis factor-α–related apoptosis-inducing ligand) induce the mitochondrial release and cytosolic accumulation of Smac/DIABLO, along with cyt c, in human acute leukemia Jurkat T cells. While it had no activity alone, ectopic overexpression of Smac/DIABLO or treatment with the N-terminus heptapeptide (Smac-7) or tetrapeptide (Smac-4) of Smac/DIABLO significantly increased Epo B– or Apo-2L/TRAIL–induced processing and PARP cleavage activity of caspase-3. This produced a significant increase in apoptosis of Jurkat cells (P < .05). Increased apoptosis was also associated with the down-regulation of XIAP, cIAP1, and survivin. Along with the increased activity of caspase-3, ectopic overexpression of Smac/DIABLO or cotreatment with Smac-4 also increased Epo B– or Apo-2L/TRAIL–induced processing of caspase-8 and Bid, resulting in enhanced cytosolic accumulation of cyt c. This was not due to increased assembly and activity of Apo-2L/TRAIL–induced DISC (death-inducing signaling complex) but dependent on the feedback activity of caspase-3. These findings demonstrate that cotreatment with the N-terminus Smac/DIABLO peptide is an effective strategy to enhance apoptosis triggered by the death receptor or mitochondrial pathway and may improve the antitumor activity of Apo-2L/TRAIL and Epo B.
ELECTRIC EARTH TRANSIENTS IN GEOPHYSICAL PROSPECTING
Authors: Statham Louis
Published: October 2002

A suddenly applied electric current is passed through the earth by means of spaced electrodes. The form of the potential transient as it appears outside the current electrodes is studied. The potential transient is extremely rapid and refined methods of recording are necessary. Means for measuring the relative times of the transient potentials received from different points are discussed. A survey taken over a known deep salt dome is shown; anomalous times of the transients are found to exist over the dome. No correlation is seen between the times of the transients and the resistivity as found by ordinary electrical methods.
THE GULF AIRBORNE MAGNETOMETER
Authors: Wyckoff R. D.
Published: October 2002

Airborne‐magnetometer operation involve two basic problems: (1) measurement of the magnetic‐field intensity; (2) navigation of the aircraft to provide the desired profile configuration and accurate mapping of the profiles flown. Currently the navigation and mapping presents the most serious problem if the operation is to be made completely airborne. A brief outline of the magnetometer instrumentation is presented, together with a discussion of the mapping problem. Examples of results are presented.
LEAST SQUARES RESIDUAL ANOMALY DETERMINATION
Authors: Agocs W. B.
Published: October 2002

The residual anomaly is defined as the deviation from the mean anomaly surface, or the regional surface. The regional surface which best fits the observed anomaly data may be determined by least squares. For the case of the simple plane, the equation of the regional would be Z = Ax+By+C, and the residual anomaly would be R=G−Z=G−(Ax+By+C), where G is the observed value at the station whose coordinates are x, y. The constants of the equation of the regional may be determined by using the normalizing equations [Formula: see text]; [Formula: see text]; [Formula: see text]. It is shown that for a symmetrical distribution of observational points about a center, the regional value at the center would be equal to [Formula: see text] and this value subtracted from the central point is the residual. Given the coordinates and the observed values, the regional may be determined, and the residual for the area calculated rapidly. An example is given of the procedure.
A VELOCITY FUNCTION INCLUDING LITHOLOGIC VARIATION
Authors: Faust L. Y.
Published: October 2002

Assuming velocity (V) a function of depth (Z), geologic time (T), and lithology (L) the resistivity log is an approach to the determination of L. Since general knowledge of water resistivity values [Formula: see text] is lacking, the values of true resistivity [Formula: see text] against [Formula: see text] were compared for 670,000 feet of section widely distributed geographically. Variations in [Formula: see text] were presumably averaged out thereby, and the results indicate that statistically [Formula: see text] and [Formula: see text] This formula was applied to an additional 270,000 feet of section more localized geographically to observe its accuracy in predicting vertical travel time. If a correction map for [Formula: see text] variations is applied the results are encouraging but less accurate than good velocity surveys. Examination of an inconclusively small amount of data with more careful measurements of [Formula: see text] suggests that accuracy comparable to direct measurement may be attainable. The cooperation of other investigators and of the electric‐logging specialists is desired.
INTERPRETATION OF RESISTIVITY DATA OVER FILLED SINKS
Authors: Cook Kenneth L. , Van Nostrand Robert G.
Published: October 2002

Solutions of Laplace’s equation in prolate and oblate spheroidal coordinates are applied to problems that arise in resistivity surveys over filled hemispheroidal sinks. Comprehensive sets of theoretical curves are presented for both horizontal and vertical profiles in the vicinity of filled sinks. The effectiveness of these theoretical curves is demonstrated not only for the interpretation of resistivity data but also for the planning of proper field techniques in resistivity surveying over such sinks. Excellent correlation between theoretical and observed field resistivity curves is shown over a shale sink in the Tri‐State lead‐zinc mining district, near Joplin, Missouri. It is shown that a filled sink can be approximated in its resistivity edge effects by 1) a vertical dike if the width of the sink is small in comparison with its length and its depth; and 2) a vertical fault if the sink is large in comparison with the electrode separation. A study of the Lee and Wenner configurations indicates that the former gives additional information that more than justifies the extra time and expense involved.
WAVE PROPAGATION IN A STRATIFIED MEDIUM
Authors: Postma G. W.
Published: October 2002

A periodic structure consisting of alternating plane, parallel, isotropic, and homogeneous elastic layers can be replaced by a homogeneous, transversely isotropic material as far as its gross‐scale elastic behavior is concerned. The five elastic moduli of the equivalent transversely isotropic medium are accordingly expressed in terms of the elastic properties and the ratio of the thicknesses of the individual isotropic layers. Imposing the condition that the Lamé constants in the isotropic layers are positive, a number of inequalities are derived, showing limitations of the values the five elastic constants of the anisotropic medium can assume. The wave equation is derived from the stress‐strain relations and the equation of motion. It is shown that there are in general three characteristic velocities, all functions of the direction of the propagation. A graphical procedure is given for the derivation of these characteristic velocities from the five elastic moduli and the average density of the medium. A few numerical examples are presented in which the graphical procedure is applied. Examples are given of cases which are likely to be encountered in nature, as well as of cases which emphasize the peculiarities which may occur for a physically possible, but less likely, choice of properties of the constituent isotropic layers. The concept of a wave surface is briefly discussed. It is indicated that one branch of a wave surface may have cusps. Finally, a few remarks are made on the possible application of this theory to actual field problems.
ELASTIC WAVE VELOCITIES IN HETEROGENEOUS AND POROUS MEDIA
Authors: Wyllie M. R. J. , Gregory A. R. , Gardner L. W.
Published: October 2002

Longitudinal wave velocities in numerous synthetic and natural porous media at room temperature and pressure have been measured. Basic characteristics of the measuring device are briefly described. Wave velocities have been found for aggregates of uniform spheres of various diameters both when dry and when saturated with water, brine, organic liquids and plastics. The effect of porosity on the wave velocity through aggregates of glass spheres saturated with plastic has been determined over the porosity range 19%–70%. Experimental measurements have been made of the effect of varying brine‐oil and brine‐gas saturations on the wave velocity through natural sedimentary rock samples. The effect of salinity and temperature on the wave velocity through sodium chloride brines has been redetermined. Results are graphically presented to show experimental relationships between wave velocity, porosity, pore content and matrix nature of sedimentary rocks. Some conclusions are drawn regarding general relationships between these factors based on the experimental results and on theoretical considerations. Through these relationships continuous velocity logs in wells can be interpreted to furnish a measure of formation porosity. Some comparisons are given between porosities derived from continuous velocity logs and found by core analysis.
VARIATION WITH DEPTH IN SHALLOW AND DEEP WATER MARINE SEDIMENTS OF POROSITY, DENSITY AND THE VELOCITIES OF COMPRESSIONAL AND SHEAR WAVES
Authors: Nafe John E. , Drake Charles L.
Published: October 2002

In a study of the dependence of the velocity of compressional waves in marine sediments upon the thickness of overburden, the velocity‐depth relationship in shelf sediments is shown to be distinctly different from that in deep basin sediments. The difference between the two cases may be illustrated by comparing the straight lines that best represent the data. These are [Formula: see text] shallow water, [Formula: see text] deep water where V is in km/sec and Z is in kilometers. Shallow and deep water are defined arbitrarily to be under 100 fathoms and over 1,500 fathoms respectively. The observed variation of average compressional velocity in the shallow and deep water sediments, taken together with the known limited range of variation of velocity for a given porosity, yields limits in turn upon the porosity‐depth dependence in the two environments. It is shown that at the same depth of overburden porosity is much greater in deep water sediments than in shallow. A physical argument is presented to show that there is implicit in the observed narrow range of variation of velocity with porosity a simple relation between porosity and rigidity. Thus quantitative estimates of shear velocity may be made from compressional velocity alone. In this way the original data are used to place rather narrow limits on the depth variation of shear velocity, porosity, and density. A number of comparisons with observation are employed to test the conclusions at each stage of the discussion.
SOME EFFECTS OF FORMATION ANISOTROPY ON RESISTIVITY MEASUREMENTS IN BOREHOLES
Authors: Kunz K. S. , Moran J. H.
Published: October 2002

It is shown that a wide class of potential problems involving anisotropic media can be transformed into equivalent problems involving only isotropic media. By means of such transformations it is possible, in a large number of cases, to determine the apparent resistivities which would be observed in anisotropic formations, using electrode‐type resistivity logging devices. Discussion is given of an infinite, anisotropic medium with and without borehole, of two semi‐infinite anisotropic beds (without borehole), and of a thin isotropic bed bounded by anisotropic adjacent formations (without borehole). An interpretation chart for the normal device is presented for thick, non‐invaded, anisotropic beds penetrated by a borehole.
RAPID COMPUTATION OF GRAVITATIONAL ATTRACTION OF THREE‐DIMENSIONAL BODIES OF ARBITRARY SHAPE
Authors: Talwani Manik , Ewing Maurice
Published: October 2002

An expression is derived for the gravity anomaly at an external point caused by a horizontal lamina with the boundary of an irregular polygon. This expression is put in a form suitable for computation by a high speed digital computer. By making the number of sides of the polygon sufficiently large, any irregular outline can be closely approximated. Any three dimensional body can be represented by contours. By replacing each contour by a polygonal lamina, the anomaly caused by it can be obtained at any external point. By a system of interpolation between contours combined with a numerical integration the gravity anomaly caused by the three‐dimensional body can be calculated to a high degree of precision. This method may also be used for rapidly computing terrain corrections on a flat earth. By making a small modification it can further be adopted for computing the terrain correction as well as local isostatic compensation on the Airy system up to the external radius of Hayford zone O on a spherical earth. The expression for the anomaly caused by a horizontal polygonal lamina is also obtained for the special case when the sides of the polygon are alternately parallel to the x- and y-axes, that is, the polygonal lamina can be divided into a number of rectangular laminae. A chart is provided for the hand computation of the gravity anomaly in this case.
MAGNETIC ANOMALIES DUE TO PRISM‐SHAPED BODIES WITH ARBITRARY POLARIZATION
Authors: Bhattacharyya B. K.
Published: October 2002

A study is made of magnetic anomalies due to prism‐shaped bodies with arbitrary polarization. Expressions of the total field and its first and second derivatives are derived on the assumption of uniform magnetization through out the body. Formulas for all possible cases in connection with a rectangular prism with vertical sides can be obtained either directly from this paper or by simple extension of the formulas given here. Using the exact expressions given in this paper, the total field and its derivatives are evaluated conveniently and rapidly with the aid of a digital computer. The effect of the dip angle anti declination of the polarization vector on the size and shape of the magnetic anomaly is then studied for the case when the earth’s normal total field vector has a dip angle of 60° and declination of 0°. With an increase in the dip angle of the polarization vector, the negative anomaly occurring on the north of the causative body diminishes in magnitude, whereas the positive and second derivative anomalies increase to maximum values and then decrease. With an increase in declination, this latter trend is repeated with the positive anomaly but the negative and second‐derivative anomalies decrease systematically. Both the positive and second‐derivative anomalies become more and more symmetrical with respect to the prismatic body with increase in either the inclination or declination of the polarization vector.
A HISTORICAL REVIEW OF ELECTRICAL PROSPECTING METHODS
Authors: Rust W. M.
Published: October 2002

The development of electrical prospecting methods from the discoveries of R. W. Fox in 1830 to recent inventions is traced briefly.
THEORY OF GRAVITY INSTABILITY WITH VARIABLE OVERBURDEN AND COMPACTION
Authors: Biot M. A. , Odé H.
Published: October 2002

The gravitational instability of a simple two‐layered medium resting on a rigid base has been treated in terms of the analog model of Biot. In order to avoid complications of purely mathematical nature which are unrelated to the physics of the process of instability and do not affect the results significantly, the analysis is presented for the two‐dimensional case. It is shown that such a system is unstable if the density contrast Δρ between the top layer (overburden) and the bottom layer (salt) is positive. The physically important parameters of the instability are the viscosity ratio and the thickness ratio between overburden and salt and the relative density contrast [Formula: see text]. These parameters determine the amplification rate of a given initial sinusoidal perturbation of wavelength L of the overburden‐salt interface. For the purpose of isolating the role of each parameter and to provide an understanding of the underlying mechanics, several tables are presented which show the influence of each of these parameters as well as the wavelength of maximum amplification rate (dominant wavelength) and the time in which a thousandfold amplification is obtained (characteristic time). This form of presentation of results is well suited to geological problems including the variable time dependence of the overburden due to gradual sedimentation. The influence of either an additional surface layer of water or a nonrigid base of high viscosity is small. The special condition of keeping the surface of the upper layer flat while the volume is held constant, termed “redistribution,” leads to an increased rate of growth and slightly longer dominant wavelength. The geologically more significant case of an instability with time‐dependent thickness and compaction of overburden is solved by introduction of an effective density [Formula: see text] of the overburden. The characteristic times and dominant wavelengths of salt structures in a salt layer of initial thickness of 1,000 m and viscosity of [Formula: see text] poises overlain by sediment of viscosity of [Formula: see text] poises are in excellent agreement with observed facts.
TWO‐DIMENSIONAL HARMONIC ANALYSIS AS A TOOL FOR MAGNETIC INTERPRETATION
Authors: Bhattacharyya B. K.
Published: October 2002

The total magnetic field values over an area can be represented exactly by a double Fourier series expansion. In this analysis, such an expansion is used to evaluate very accurately the fields continued downward and upward from the plane of observation and the vertical derivatives of the total field. This harmonic expansion of the anomalous total field makes it possible to calculate, with exceptional accuracy, the field reduced to the magnetic pole and its second derivative. The results of the calculations are free from the effect of the inclination of the earth’s main geomagnetic field and that of the polarization vector, at all magnetic latitudes and for all possible directions of polarization. In order to determine the influence of remanence on the above field, a number of anomalies caused by rectangular block‐type bodies with known polarization are reduced to the magnetic pole, correcting only for the obliquity of the earth’s normal field. It is concluded from a study of these anomalies that the interpretation of magnetic data based on the assumption of rock magnetization due solely to induction in the earth’s field may yield erroneous results, particularly when remanence is important.
EFFECT OF WAVELENGTH FILTERING ON THE SHAPE OF THE RESIDUAL ANOMALY
Authors: Ulrych T. J.
Published: October 2002

Recently Skeels (1967) has considerably clarified the concept of the term “residual gravity” and has proposed a modified polynomial fitting method as a computational scheme. In the article Skeels refers to wavelength (or wavenumber) filtering discussed by Byerly (1965). Wavelength filtering has been recently applied by Zurflueh (1967) to the determination of residual aeromagnetic anomalies. Although Zurflueh compares wavelength filtering and least‐squares polynomial fitting methods and mentions the pseudo anomalies introduced by the latter method, he does not discuss the effect of wavelength filtering on the shape of the residual anomaly.
PREDICTIVE DECONVOLUTION: THEORY AND PRACTICE
Authors: Peacock K. L. , Treitel Sven
Published: October 2002

Least‐squares inverse filters have found widespread use in the deconvolution of seismograms. The least‐squares prediction filter with unit prediction distance is equivalent within a scale factor to the least‐squares, zero‐lag inverse filter. The use of least‐squares prediction filters with prediction distances greater than unity leads to the method of predictive deconvolution which represents a more generalized approach to this subject. The predictive technique allows one to control the length of the desired output wavelet, and hence to specify the desired degree of resolution. Events which are periodic within given repetition ranges can be attenuated selectively. The method is thus effective in the suppression of rather complex reverberation patterns.
THE ATTENUATION OF COMPRESSIONAL WAVES IN MARINE SEDIMENTS
Authors: McCann C. , McCann D. M.
Published: October 2002

A number of mechanisms have been proposed to account for the attenuation of compressional waves in water‐saturated sediments. These include viscous losses between the particles and the fluid, and “solid friction” losses between the particles. The mechanisms are discussed and it is shown how the low values of attenuation observed in pure clays arise from the electrical interaction forces between the surface‐active particles. It is proposed that the attenuation in clay‐ and silt‐size sediments (up to 6 phi mean diameter) arises from viscous interaction between the clay‐water “fluid” and the non‐surface‐active particles. Both new and published experimental measurements indicate that the proposed mechanism is valid, at least in a frequency range 30 to 370 kHz. For sediments of mean particle diameter greater than 6 phi, both new and published experimental results are presented to show that, although under the circumstances of a very well sorted sediment under zero overburden pressure a viscous dissipation mechanism may be dominant, the “solid friction” mechanism is dominant for poorly sorted sediments buried to a depth of 2 m.
A SIMPLE THEORY FOR SEISMIC DIFFRACTIONS
Authors: Trorey A. W.
Published: October 2002

Existing diffraction theory is often cast in such a way as to preclude a ready qualitative understanding of diffraction phenomena. This difficulty can be overcome by making simplifying but realistic approximations which permit the diffractive response of an arbitrary subsurface with point‐source excitation to be obtained in a simple closed form. The main approximations are that the subsurface behaves as an acoustic medium, that its average velocity is constant, and that its reflectivity is low. An objective of this paper is to provide the field interpreter with a practical understanding of diffraction behavior.
A SYSTEM FOR RAPID DIGITAL AEROMAGNETIC INTERPRETATION
Authors: Hartman Ronald R. , Teskey Dennis J. , Friedberg Jeffrey L.
Published: October 2002

In this paper, we describe a system for the collection and interpretation of aeromagnetic data. The great interdependence of the detection instrumentation, the navigation instrumentation, the compilation procedures, and the interpretation techniques is defined. Doppler radar is the basis for aircraft navigation; it drives the recording devices to produce spatial‐domain data. A digital system provides a means for rapid computer interpretation. A distinction is made between data‐processing techniques that aid in interpretation and those that are involved in the actual definition of magnetic anomalies in terms of the horizontal and vertical position of the causative bodies. The computerized interpretation technique described herein is an extension of a technique first described by S. Werner of the Geological Survey of Sweden. Depths are calculated for all geologic events with some elongation, regardless of the events’ strike, dip, and remanent magnetization; and the calculations are valid at any magnetic inclination. Our system is illustrated with model studies and actual examples.
VELOCITY AND ATTENUATION OF SEISMIC WAVES IN TWO‐PHASE MEDIA: PART II. EXPERIMENTAL RESULTS
Authors: Kuster Guy T. , Toksöz M. Nafi
Published: October 2002

The velocity and attenuation of ultrasonic waves are measured in suspensions of solid spherical particles in fluid matrices as a function of the concentration of inclusions. Polystyrene and glass beads were used as inclusions and they were suspended in pure water, oil, or acetylene tetrabromide. Velocities were measured by a pulse propagation technique. Attenuation in mixtures was measured relative to attenuation in pure matrix fluid. The observed velocities were compared to theoretical values calculated using six different models. The closest agreement is obtained for the dynamic interaction model given in Part I by Kuster and Toksöz (1974) and for the Reuss model. The theoretical formulas for the attenuation in composite media are given. The observed attenuation agrees reasonably well with the theoretical values computed by including geometrical scattering, viscous absorption in the fluid matrix, and the anelasticity of the solid inclusions.
A MODIFIED PSEUDOSECTION FOR RESISTIVITY AND IP
Authors: Edwards L. S.
Published: October 2002

Dipole‐dipole induced‐polarization measurements are commonly presented as pseudosections, but results using different dipole lengths cannot be combined into a single pseudosection. By considering the theoretical results for simple earth models, a unique set of relative depth coefficients is empirically derived, such that measurements with different array parameters will “mesh” smoothly into a combined pseudosection. Application of these coefficients to a number of theoretical and field cases shows that they give reasonable results when applied to more complicated models. The empirical coefficients are compared with Roy’s theory of “depth of investigation characteristic,” and support that theory, if a modified definition of “effective depth” is accepted. This leads to an absolute depth scale for the modified pseudosection. It is shown that rough estimates of the depth to the top of an anomalous body can be made directly on the pseudosection, at true vertical scale. This definition of effective depth is applied to other electrode arrays. It is shown, by examples, that the resulting pseudosections give consistent estimates of depth to top, within the characteristic anomaly patterns of each array. The effective depths for various arrays are compared; the results agree with the traditional applications of each array.
COMPUTER MODELING IN GRAVITY AND MAGNETIC INTERPRETATION
Authors: Bhattacharyya B. K.
Published: October 2002

Computation of anomalous gravity and magnetic fields generated by various models is a necessary step if techniques of curve‐matching are to be used for quantitative interpretation of potential field data. Recently developed methods show that anomalous magnetic and gravity fields are completely determined by the divergence of magnetization and the first vertical derivative of density, respectively. Using these methods, efficient algorithms can be developed for computing potential field anomalies caused by arbitrary distribution of magnetization and density in an irregularly shaped body. Automatic iterative procedures are normally employed in the space domain for estimating parameters of the selected model that yield a best‐fit anomaly curve for a set of discrete observed data. Examples of application of the Newton‐Raphson method, Marquardt method, and the Powell algorithm to the interpretation of magnetic data are presented and discussed. Amplitude and energy spectra of the anomalous fields are also used conveniently in many cases for systematic estimation of average and individual depths, horizontal and vertical extents, and density or magnetization contrasts of causative bodies in a bounded region. Some of these frequency‐domain approaches are found to have many useful applications.
Synthetic sonic logs—a process for stratigraphic interpretation
Authors: Lindseth R. O.
Published: October 2002

Modern seismic reflection data may be processed to approximate closely the reflection coefficient series of a sedimentary section. Inversion of the series will produce a low‐cut filtered impedance log. Extension of the technique to include density correction and replacement of missing low‐frequency components leads to generation of a synthetic sonic log having dimensions and characteristics similar to a conventional borehole sonic log. A synthetic sonic log section provides several advantages over conventional seismic sections, particularly for stratigraphic exploration. Direct depth display largely eliminates the vertical scale distortion inherent in time sections and simplifies integration with other subsurface data. Resolution is generally improved. The process is well adapted to automated generation of stratigraphic sections. Individual rock units are mapped by contours of constant transit‐time, to show facies changes and depositional sequences in detail. The detailed measurements of velocity may be used to interpret rock type. Comparison of synthetic sonic log sections to the conventional seismic data from which they were derived, clearly demonstrates improved understanding of subsurface geology.
Cross‐borehole electromagnetic probing to locate high‐contrast anomalies
Authors: Lytle R. J. , Laine E. F. , Lager D. L. , Davis D. T.
Published: October 2002

Electromagnetic (EM) probing between boreholes is useful for locating high‐contrast geophysical anomalies such as a tunnel. Theoretical and experimental studies of EM field interaction with a tunnel show that minima in the received signal can be used for locating the tunnel. The theoretical studies show that as a transmitter and receiver are lowered in separate boreholes, the minima can be interpreted easily to yield both the lateral and vertical positions of the tunnel. The main mechanism of EM field interaction with the tunnel appears to be diffraction, and the spatial variation of the field strength is affected by the tunnel shape. Frequencies from 10 to 70 MHz were studied to assess the usable frequencies. The field in the receiver borehole was an effective diagnostic when a half‐wavelength in the surrounding medium was less than or equal to the diameter of the tunnel. EM probing at two test sites gave the locations of tunnels within 1 ft of the surveyed locations.