bluuebunny/crossref_metadata_2025 huggingface dataset:
Nasal and lower airway level of nitric oxide in children with primary ciliary dyskinesia
Authors: Karadag B , James AJ , Gultekin E , Wilson NM , Bush A
Published: October 2002

Exhaled nitric oxide can be detected in exhaled air and is readily measured by chemiluminescence. It is thought to be involved in both the regulation of ciliary motility and host defence. Recently, upper airway NO has been found to be reduced in a small number of children with primary ciliary dyskinesia (PCD) and its measurement has been recommended as a diagnostic test for this condition. The aim of this study was to compare the levels of NO in the upper and lower airways in a larger number of children with proven PCD with those found in healthy children. Exhaled NO was measured in the upper airway by direct nasal sampling during a breath-hold and in the lower airway as the end-tidal plateau level, using a chemiluminescence NO analyser. Upper airway NO levels were significantly lower in PCD (n = 21) than in the healthy children (n = 60) (mean +/-SD, 97+/-193, 664+/-298 parts per billion (ppb), respectively, p<0.0001). In PCD, the lower airway NO levels were also reduced (2.17+/-1.18, 5.94+/-3.49 ppb, respectively, p<0.0001). The levels were not associated with steroid use and did not correlate with lung function. Although there was some overlap between normal children and those with primary ciliary dyskinesia with regard to lower airway NO, nasal NO discriminated between the two groups in all but one child in each group. Measurement of nasal NO therefore may be a useful screening test for primary ciliary dyskinesia.
Sampling of exhaled nitric oxide in children: end-expiratory plateau, balloon and tidal breathing methods compared
Authors: Jobsis Q , Schellekens SL , Kroesbergen A , Hop WC , de Jongste JC
Published: October 2002

The aim of this study was to compare exhaled nitric oxide concentrations obtained during controlled slow exhalation, presently considered as the method of choice, with two sampling methods that are easily performed by children: blowing air into a balloon and tidal breathing through a mouthpiece. One hundred and one well controlled, stable allergic asthmatic children (median age 11.7 yrs) performed the following tasks in duplicate: 1) exhalation from total lung capacity through a mouthpiece against a resistor with a standardized flow rate of 20% of the subject's vital capacity per second, using a biofeedback system; 2) a single deep exhalation into an NO-impermeable mylar balloon; and 3) tidal breathing through a low resistance mouthpiece over 2 min. NO was measured using a chemiluminescence analyser. Twenty-nine children (29%) were not able to perform a constant-flow exhalation of at least 3 s. All children performed the balloon and tidal breathing methods without difficulty. NO concentrations (means +/-SEM) were 5.3+/-0.2 parts per billion (ppb) at the end-expiratory plateau, 5.2+/-0.3 ppb in balloons (intraclass correlation coefficient (r(i)) = 0.73) and 8.0+/-0.4 ppb during tidal breathing (p<0.001, r(i) = 0.53 compared to plateau values). Mean values of NO during tidal breathing increased significantly with time, suggesting increasing contamination with nasal air. It was concluded that, in asthmatic children, the end-expiratory plateau concentration of nitric oxide during exhalation at 20% of the vital capacity per second is similar to the values obtained with the balloon method, with satisfactory agreement, but differs from values obtained during tidal breathing. The balloon method is cheap, simple and offers the interesting possibility to study exhaled nitric oxide in young children independently of the presence of a nitric oxide analyser.
Ozone-induced lung function decrements do not correlate with early airway inflammatory or antioxidant responses
Authors: Blomberg A , Mudway IS , Nordenhall C , Hedenstrom H , Kelly FJ , Frew AJ , Holgate ST , Sandstrom T
Published: October 2002

This study sought to clarify the early events occurring within the airways of healthy human subjects performing moderate intermittent exercise following ozone challenge. Thirteen healthy nonsmoking subjects were exposed in a single blinded, crossover control fashion to 0.2 parts per million (ppm) O3 and filtered air for 2 h, using a standard intermittent exercise and rest protocol. Lung function was assessed pre- and immediately post-exposure. Bronchoscopy was performed with endobronchial mucosal biopsies, bronchial wash (BW) and bronchoalveolar lavage (BAL) 1.5 h after the end of the exposure period. Respiratory tract lining fluid (RTLF) redox status was assessed by measuring a range of antioxidants and oxidative damage markers in BW and BAL fluid samples. There was a significant upregulation after O3 exposure in the expression of vascular endothelial P-selectin (p<0.005) and intercellular adhesion molecule-1 (p<0.005). This was associated with a 2-fold increase in submucosal mast cells (p<0.005) in biopsy samples, without evidence of neutrophilic inflammation, and a decrease in BAL fluid macrophage numbers (1.6-fold, p<0.005), with an activation of the remaining macrophage subset (2.5-fold increase in % human leukocyte antigen (HLA)-DR+ cells, p<0.005). In addition, exposure led to a 4.5-fold and 3.1-fold increase of reduced glutathione (GSH) concentrations, in BW and BAL fluid respectively (p<0.05), with alterations in urate and alpha-tocopherol plasma/RTLF partitioning ratios (p<0.05). Spirometry showed reductions in forced vital capacity (p<0.05) and forced expiratory volume in one second (p<0.01), with evidence of small airway narrowing using forced expiratory flow values (p<0.005). Evidence was found of O3-induced early adhesion molecule upregulation, increased submucosal mast cell numbers and alterations to the respiratory tract lining fluid redox status. No clear relationship was demonstrable between changes in these early markers and the lung function decrements observed. The results therefore indicate that the initial lung function decrements are not predictive of, or causally related to the O3-induced inflammatory events in normal human subjects.
Antioxidant consumption and repletion kinetics in nasal lavage fluid following exposure of healthy human volunteers to ozone
Authors: Mudway IS , Blomberg A , Frew AJ , Holgate ST , Sandstrom T , Kelly FJ
Published: October 2002

To obtain information on the real-time events occurring within human respiratory tract lining fluids (RTLFs) during ozone exposure, sequential nasal lavage was performed on 13 human volunteers exposed on separate occasions to 0.2 parts per million O3 and filtered air (2-h exposures, with intermittent exercise). Nasal lavage was performed and blood samples obtained at four time points throughout each exposure: pre-exposure (Pre-E), 1 h into exposure (1h-E), immediately post-exposure (0h-PE) and 1 h post-exposure (1h-PE). Endobronchial mucosal biopsies were obtained at 1.5 h-post exposure (1.5h-PE). Nasal RTLF neutrophilia was not apparent during, or 1.5 h after, 03 exposure. Furthermore, activation of the pre-existing neutrophil population did not occur. Airway permeability was not altered by this 03 exposure regimen. Sequential lavage resulted in significant washout of RTLF ascorbic acid, reduced glutathione, extracellular superoxide dismutase and myeloperoxidase at 1h-E, 0h-PE and 1.5h-PE relative to baseline Pre-E values. In contrast, RTLF uric acid (UA), total protein and albumin concentrations did not display washout kinetics. Of the antioxidants examined, only UA was clearly depleted by 03, concentrations, falling by 6.22 micromol x L(-1) at 1h-E, compared with 1.61 micromol x L(-1) (p<0.01) during control air exposure. The establishment of a new pseudo-steady-state concentration of RTLF UA (70% of Pre-E values) during the second hour of O3 exposure was coincident with a small but significant increase in plasma UA concentration (19.27 (O3) versus 1.95 micromol x L(-1) (air), p<0.05). These data demonstrate that inhalation of 0.2 parts per million 03 results in the depletion of nasal respiratory tract lining fluid uric acid and that this regional loss of uric acid leads to a small increase in plasma uric acid concentration. Whilst the reaction of uric acid with inspired 03 may confer protection locally, the role of upper airway uric acid as a sink for inhaled O3 is not supported by these findings.
Pulmonary surfactant in health and human lung diseases: state of the art
Authors: Griese M
Published: October 2002

Pulmonary surfactant is a complex and highly surface active material composed of lipids and proteins which is found in the fluid lining the alveolar surface of the lungs. Surfactant prevents alveolar collapse at low lung volume, and preserves bronchiolar patency during normal and forced respiration (biophysical functions). In addition, it is involved in the protection of the lungs from injuries and infections caused by inhaled particles and micro-organisms (immunological, non-biophysical functions). Pulmonary surfactant can only be harvested by lavage procedures, which may disrupt its pre-existing biophysical and biochemical micro-organization. These limitations must always be considered when interpreting ex vivo studies of pulmonary surfactant. A pathophysiological role for surfactant was first appreciated in premature infants with respiratory distress syndrome and hyaline membrane disease, a condition which is nowadays routinely treated with exogenous surfactant replacement. Biochemical surfactant abnormalities of varying degrees have been described in obstructive lung diseases (asthma, bronchiolitis, chronic obstructive pulmonary disease, and following lung transplantation), infectious and suppurative lung diseases (cystic fibrosis, pneumonia, and human immunodeficiency virus), adult respiratory distress syndrome, pulmonary oedema, other diseases specific to infants (chronic lung disease of prematurity, and surfactant protein-B deficiency), interstitial lung diseases (sarcoidosis, idiopathic pulmonary fibrosis, and hypersensitivity pneumonitis), pulmonary alveolar proteinosis, following cardiopulmonary bypass, and in smokers. For some pulmonary conditions surfactant replacement therapy is on the horizon, but for the majority much more needs to be learnt about the pathophysiological role the observed surfactant abnormalities may have.
Pseudochylothorax in pleural effusion due to coronary artery bypass surgery
Authors: Garcia-Pachon E , Fernandez LC , Lopez-Azorin F , Padilla-Navas I
Published: October 2002

This study describes a 64-yr-old male with a chronic left pleural effusion following a coronary artery bypass 3 yrs earlier. On thoracocentesis, turbid fluid was obtained with crystals of cholesterol on microscopic examination, establishing the diagnosis of pseudochylothorax. The pleural fluid cholesterol level was 207 mg x dL(-1) (5.36 mmol x L(-1)). This is the first report of pseudochylothorax in a chronic pleural effusion due to coronary artery bypass surgery.
Snoring and excessive daytime somnolence among Polish middle-aged adults
Authors: Zielinski J , Zgierska A , Polakowska M , Finn L , Kurjata P , Kupsc W , Young T
Published: October 2002

There is considerable interest in the association of snoring and health consequences that have been linked to more severe sleep-disordered breathing, including obstructive sleep apnoea syndrome. The goal of this investigation was to assess the independent association of heavy, habitual snoring and daytime sleepiness. For this, a cross-sectional, population based study of snoring, sleepiness and other factors was conducted using the Warsaw sample of the Multinational Monitoring of Trends and Determinants of Cardiovascular Diseases (MONICA) study, a population-based multicentre study of cardiovascular disease. The well-defined MONICA sample of middle-aged males and females also allowed estimation of age- and sex-specific prevalences of habitual snoring in Polish adults. Data on self-reported snoring frequency and loudness, and daytime sleepiness using the Epworth Sleepiness Scale (ESS) and other questions, were collected with a postal questionnaire. Seventy-nine per cent of the MONICA sample completed the questionnaire, yielding a total of 1,186 participants. Of the total sample, 27% of the females and 48% of the males reported habitual snoring ("often" or "always"). There was an independent association of habitual snoring and excessive daytime sleepiness (EDS), sleepiness that interfered with work and with increasing ESS scores. Habitual snorers were 5.8 and 3.1 times more likely to report EDS in active and passive situations, respectively, compared to nonsnorers (all p<0.01). It is concluded that habitual snorers, most of whom are probably unlikely to have frank sleep apnoea syndrome, are at substantial risk for daytime sleepiness. These findings add support to the hypothesis that simple snoring is not benign and underscores the need for further research on health outcomes associated with this prevalent condition.
“Geophysical Prospecting,” Reports on Progress in Physics, vol. ii, pp. 97–128. By E. Lancaster‐Jones. Published by the Physical Society, London (1936).
Authors: Slotnick M. M.
Published: October 2002

This chapter on Geophysical Prospecting is a brief summary of the methods most commonly used in applied geophysics at the present time. It is mostly descriptive in content, although some elementary theoretical matters are discussed, and, in a few cases, brief historical remarks are made. To the practicing geophysicist, the chapter will serve merely as light reading, but to the scientist who wants a quick perspective idea of the methods of applied geophysics, it will be of some interest.
A DISCUSSION OF STEEP‐DIP SEISMIC COMPUTING METHODS—II
Authors: Rice R. B.
Published: October 2002

This paper is a continuation of a previous one in which the author gave a comparison of several commonly used steep‐dip seismic computing techniques on the basis of the horizontal displacements and depths of the reflection points they produce, assuming a rather “slow” parabolic increase of velocity with depth. In this paper, the comparison of these methods is extended to the case of a second and considerably “faster” velocity function and to the computation of a reflecting horizon through a fault zone. In addition, two other straight‐path methods and three purely mathematical methods are introduced and compared in the same manner with the curved‐path method.
NOTE ON WELL‐SHOOTING DATA AND LINEAR INCREASE OF VELOCITY
Authors: Slotnick M. M. , Brooks J. A. , Redding V. L.
Published: October 2002

The problem of converting well‐shooting data into parameters necessary for interpretation is an important one. When the data seem to lend themselves to the hypothesis of a linear increase of velocity with depth, i.e., [Formula: see text], the problem is one of determining the constants [Formula: see text] and a from the data.
COMBINED ANALYSIS OF GRAVITY AND MAGNETIC ANOMALIES
Authors: Garland G. D.
Published: October 2002

The relationship betwen gravity and magnetic anomalies is investigated. It is shown that the ratio of the anomalous susceptibility to the anomalous density of an unknown body may be determined from gravimeter and vertical magnetometer observations, independent of assumptions as to the depth or form of the body. The use of this ratio in identifying the rock material of the body is discussed, and illustrated by applying the method to a well‐known case.
THE INVESTIGATION OF EARTH RESISTIVITIES IN THE VICINITY OF A DIAMOND DRILL HOLE
Authors: Clark A. R. , Salt D. J.
Published: October 2002

The method of electrical images has been used to derive an expression for the difference in potential between two points close to a good conducting sphere in a poor conducting medium. The results indicate that the presence of a conducting ore body of commercial size near a drill hole can be detected by suitable electrical measurements made in the hole. The results of a test of the method in a drill hole near a small conducting sulphide ore body are given.
SAFETY AND GEOPHYSICAL EXPLORATION
Authors: Sorge Bart W.
Published: October 2002

The safety and accident prevention record of geophysical operations has substantially improved during the last decade. A well‐planned safety and accident prevention program which has the full support of all parts of an organization will produce results. Many advantages can be gained by improving the cooperation in safety matters among operators of geophysical crews.
HIGH MAGNETIC EFFECT OF LATERITIC SOIL IN CUBA
Authors: Tucker Paul M.
Published: October 2002

During the course of a conventional vertical magnetic survey in Cuba, it was found that many stations underlain by lateritic red soil gave unusually erratic values. A susceptibility determination of the soil showed it to have a value of [Formula: see text] cgs.
A LEAST SQUARE METHOD FOR GRAVITY METER BASE STATIONS
Authors: Pentz H. H.
Published: October 2002

Two applications of the Method of Least Squares in determining the most probable values from gravity meter base station applications are considered. One is an approximation, the degree of approximation depending on the number of base stations. The second is a rigorous application of the Method of Least Squares in obtaining the most probable values for an expanding base station network.
THE FIELD OF A MAGNETIC DIPOLE IN THE PRESENCE OF A CONDUCTING SPHERE
Authors: March H. W.
Published: October 2002

Formulas are derived for the components of the distorted field of a magnetic dipole in the presence of a conducting sphere in a homogeneous medium. In the method employed the field is resolved into two partial fields for the first of which the radial component of the magnetic vector vanishes and for the second of which the radial component of the electric vector vanishes. From the general formulas approximate formulas are derived for the field components in the special case in which the conductivity of the medium is low, the radius of the sphere is not too large and both the dipole and the observer are in the vicinity of the sphere. These approximate formulas are within limits applicable to the problem of locating a spherical body of ore buried in a mass of rock.
CASE HISTORY OF WILD GOOSE GAS FIELD, BUTTE COUNTY, CALIFORNIA
Authors: Matjasic Wallace L.
Published: October 2002

The discovery well of the Wild Goose gas field was drilled and completed in 1951 on a structure located by a reflection seismograph survey conducted in 1950. An additional seismograph survey was made subsequent to discovery to define the structure better for further development. The illustrations include two seismic cross sections, a contour map based on the original seismic reflection data, an aeromagnetic map, a structure contour map, and an electric log of the discovery well. The producing sands are in an interval between the Forbes shale of Upper Cretaceous age and the overlying Capay shale of Eocene age.
ABNORMAL VELOCITIES IN SEDIMENTARY BEDS IN EASTERN UTAH
Authors: Smith A. L. , Wilson John H.
Published: October 2002

Velocity determinations at wells and refraction shooting in the area indicate abnormally high velocities in Utah. The following conclusions are reached: (1) these high velocities are related to hardening due to incipient metamorphism after deposition; (2) this condition has an adverse effect on the quality of reflections; (3) it interferes with interpretation of refraction data; (4) it may be an index of unfavorable condition for accumulation of oil or gas.
ORTHOGONAL POLYNOMIALS: THEIR USE IN ESTIMATING THE REGIONAL EFFECT
Authors: Oldham C. H. G. , Sutherland D. B.
Published: October 2002

The examination of experimental data for significant trends by orthogonal polynomials is well known in statistics. The method is adapted here to the estimation of regional trends in potential field observations, and two characteristically‐different gravity maps are analyzed. The method is found to agree closely with a graphical solution in an area of fairly smooth contours, and to give a reasonable solution in an area where the graphical method would be difficult to apply. It is proposed that the orthogonal polynomials could also be adapted to evaluating total mass and to interpreting second derivative maps.
USE OF RECIPROCITY THEOREM FOR COMPUTATION OF LOW‐FREQUENCY RADIATION PATTERNS
Authors: White J. E.
Published: October 2002

Starting with a simple word statement of the reciprocity which exists between forces and displacements in a general elastic solid, it is shown that low‐frequency radiation of shear and compressional waves from relatively complex sources can be obtained by solving relatively simple problems in static elasticity. Illustrative examples include radiation from radial and tangential pairs of forces acting on the wall of a cylinder, pressure in a finite cylinder, and a pair of radial forces in a hole in a plate. For the last case, measurements in a plexiglas plate compare favorably with computations.
THE REFLECTION OF RAYLEIGH WAVES BY A HIGH IMPEDANCE OBSTACLE ON A HALF‐SPACE
Authors: Fredricks R. W. , Knopoff L.
Published: October 2002

The reflection of a time‐harmonic Rayleigh wave by a high impedance obstacle in shearless contact with an elastic half‐space of lower impedance is examined theoretically. The potentials are found by a function—theoretic solution to dual integral equations. From these potentials, a “reflection coefficient” is defined for the surface vertical displacement in the Rayleigh wave. Results show that the reflected wave is π/2 radians out of phase with the incident wave for arbitrary Poisson’s ratio. The modulus of the “reflection coefficient” depends upon Poisson’s ratio, and is evaluated as [Formula: see text] for σ=0.25.
GEOPHYSICAL STUDY OF SUBSURFACE STRUCTURE IN SOUTHERN OWENS VALLEY, CALIFORNIA
Authors: Kane M. F. , Pakiser L. C.
Published: October 2002

Gravity and seismic measurements in southern Owens Valley, California, have outlined a deep subsurface trough, bounded throughout the greater part of its length by steep faults. Depths to the bedrock floor along the central part of the valley range from 3,000 to 9,000 ft below the surface. The subsurface trough is divided into two parts, a narrow channel‐like depression near Lone Pine bounded by northwest‐trending faults, and a broad basin at Owens Lake bounded by a more complex series of border faults. The bedrock ridge that crops out to form Alabama Hills is shown to extend from Independence to the north edge of Owens Lake, nearly twice its visible extent. The main direction of faults that have formed the valley is northwest; subsidiary faults trend north, northeast, and east. A fairly sharp velocity boundary within the Cenozoic valley deposits suggests a change in the rate and character of deposition which was probably the result of renewed uplift in the nearby mountains.
ON THE PRINCIPLES OF GEOCHEMICAL OIL PROSPECTING
Authors: Stegena L.
Published: October 2002

The geochemical prospecting method is based upon the circumstance that the gases of the oil reservoirs migrate vertically as demonstrated by sensitive analytical techniques. Some unsatisfactory results and the criticism raised concerning the method have made necessary the investigation of the fundamental principles of the process. Gas migration is caused partly by differences in concentration, partly by differences in pressure. The migration caused by the former factor is termed diffusion, that caused by the latter one is called effusion. This paper attempts the quantitative treatment of diffusion. The results of this treatment are as follows: (1) In case the reservoir is situated at a great depth and in case the superincumbent layers are highly impermeable, a time interval is necessary to reach steady‐state diffusion which is significantly above the lifetime of the reservoirs; (2) In other cases, where the depth is not too great, or the superincumbent layers are fairly permeable, a steady‐state diffusion has to be reckoned with.
MAGNETO‐TELLURIC SOUNDING THREE‐LAYER INTERPRETATION CURVES
Authors: Yungul S. H.
Published: October 2002

To interpret the magneto‐telluric sounding data in terms of layering in the subsurface, one needs a catalog of “standard” curves. The purpose of this paper is to present such a catalog for the three‐layer cases. The calculations were done by incorporating the formulas given by Cagniard (1953) into a digital computer program. The catalog consists of 117 apparent‐resistivity‐vs‐period curves representing ten resistivity combinations. In each case the third, semi‐infinite medium represents the “basement” with infinite resistivity. In addition, a set of two‐layer curves for the total range of resistivity combinations is also given. The procedure in using the curves is briefly explained.
AMBIGUITY IN GEOPHYSICAL INTERPRETATION
Authors: Roy Amalendu
Published: October 2002

The question of uniqueness or otherwise of the various geophysical methods has been looked into from a general point of view. A method is theoretically determinate or indeterminate according as the totality of unknowns is smaller or greater than that of the independent measurables. While all natural field methods fall in the latter category, all applied field methods do not necessarily come under the former. Actual interpretations, however, cannot make any use of the theoretical uniqueness even where it exists and must depend on simplifying but permissible hypotheses based on extraneous information. These hypotheses are found to be surprisingly similar in all geophysical methods.
EÖTVÖS CORRECTIONS FOR A MOVING GRAVITY METER
Authors: Glicken Milton
Published: October 2002

When making gravity measurements with a moving meter, the Eötvös correction is often the limiting factor in the precision of the entire system. Nomograms are presented showing the error to be expected in the Eötvös correction for errors of various sizes in the determination of ground speed, heading, and latitude of the vehicle.
REGIONALS AND RESIDUALS IN SEISMIC PROSPECTING FOR STRATIGRAPHIC FEATURES
Authors: Dobrin M. B. , Rimmer W. G.
Published: October 2002

Many geological features associated with oil accumulation show up on seismic maps as interruptions of regional trends rather than as true structural closures. Among such features are reefs, which are often best detected by draping of overlying formations; erosional escarpments which truncate porous limestone beds on their updip sides; and buried ridges which cause productive stratigraphic buildups in overlying beds. In the presence of regional tilting, seismic indications from such features can be so obscured that special data‐processing techniques are required to make them readily recognizable on seismic maps. The problem here is very similar to that of separating gravity and magnetic effects of features having economic interest from regional background. Residual techniques developed for accomplishing this type of separation can be applied advantageously to seismic data where regional structure obscures significant anomalies. Both contour‐smoothing or grid methods can be used depending on the nature of the problem and the preference of the interpreter. As with gravity or magnetics, the grid methods are particularly adaptable for high‐speed electronic computation. Some examples are shown where regional effects are removed from seismic maps over known reefs and productive erosional escarpments by techniques using electronic computation. A somewhat different approach is necessary when it is desired to remove the effect of velocity variation from time maps by treating the velocity function as a regional effect. Here the regional is multiplicative rather than additive and cross‐product terms must be taken into account. By relating the time maps and velocity maps using this approach, the principal hazards of using time maps for interpretation can be avoided.
THREE‐DIMENSIONAL FILTERING WITH AN ARRAY OF SEISMOMETERS
Authors: Burg John P.
Published: October 2002

The development of the Wiener linear least‐mean‐square‐error processing theory for seismic signal enhancement through use of a two‐dimensional array of seismometers leads to the theory of three‐dimensional filtering. The array processing system for this theory consists of applying individual frequency filters to the outputs of the seismometers in the array before summation. The basic design equations for the optimum frequency filters are derived from the Wiener multichannel theory. However, the development of the three‐dimensional frequency and vector‐wave‐number‐filtering theory results in a physical understanding of generalized linear array processing. The three‐dimensional filtering theory is illuminated by a theoretical problem of P‐wave enhancement in the presence of ambient seismic noise. An analysis of the results shows why optimum three‐dimensional filtering gives greater signal‐to‐noise ratio improvements than achieved by conventional array processing techniques.
RECENT DEVELOPMENTS IN LABORATORY ORIENTATION OF CORES BY THEIR MAGNETIC POLARITY
Authors: Lynton Edward D.
Published: October 2002

During the past year further experimental work has increased the applicability of this method of orienting well cores by their magnetic polarity so that definite results now total approximately 60% of all cores tested, the presence or lack of heavy mineral grains being the depending factor. The most important developments have been, first, the elimination of human errors by making the recording apparatus entirely automatic and foolproof; second, the introduction of automatic and combined forward and reverse runs on cores, which enables the operator to distinguish definitely between polarized mineral grains and material with susceptibility only.
SEISMIC NOISE ATTENUATION IN UNCONSOLIDATED MATERIAL
Authors: Sax Robert L. , Hartenberger Royal A.
Published: October 2002

The amplitude of ambient earth noise is investigated as a function of depth for several models. The noise radiating in the layers is described hypothetically by combinations of Rayleigh‐wave modes with a prescribed form of energy partition. The anomalously low shear velocity of alluvium or weathered zones at the earth’s surface tends to produce larger amplitudes (+6 db) at the free surface, and smaller amplitudes (as much as −20 db) at the base, as compared to an arbitrarily defined “continental” structure consisting only of the more competent rocks. Results further indicate that the low‐velocity layers must reach a critical thickness before large attenuations at depth can be expected.
REFLECTION SEISMIC CRUSTAL STUDIES
Authors: Dix C. H.
Published: October 2002

Recordings taken in a region having a very thin sedimentary section (less than 100 m thick) with normal reflection prospecting equipment, using 100 to 300 kg of explosive in holes less than 10 m deep, with geophone spreads 580 m long set from two to 15 km from the shot, show events most easily interpretable as reflections. If the reflection interpretation is accepted and multiple reflections are too weak to be observed, then there are many reflectors of low dip between 8‐ and 35‐km depth in this region. The strongest and most consistent group of events in the 22 recordings arrives at about 8 sec and corresponds to a depth agreeing approximately with the crustal depth obtained by refraction methods across this region. It is emphasized that the reflection view and the refraction view may be essentially different; the latter being insensitive to low‐velocity layers and to thin, high‐velocity layers such as sills might present, whereas the former is insensitive to a gradual transition over a kilometer of depth which may occur at the crustal base. Thus the possibility exists that the reflection and refraction techniques may give wholly or partially independent views of crustal structure. The inherent inaccuracy of head‐wave methods appears to drive us toward the reflection techniques to advance our knowledge on this problem in the future. This approach is still very difficult except under favorable circumstances.
MULTI‐REFLECTED HEAD WAVES IN A SINGLE‐LAYERED MEDIUM
Authors: Nakamura Yosio
Published: October 2002

The propagation characteristics of surface‐reflected head waves have been studied experimentally using two‐ dimensional, Plexiglas‐aluminum and polystyrene‐aluminum, single‐layer models. In addition to the contributions from the reflected refractions (with reflections near the source) and the refracted reflections (with reflections near the receiver) those from the refraction‐reflection intermixtures (with reflections midway in the refraction path) have been found to be significant, resulting in a slight reinforcement of the surface‐reflected head waves with increasing distance. The phase relations of the arrivals have been examined by computing the Fourier transforms of the observed waveforms. It has been found that, relative to the principal head‐wave arrival, the surface‐reflected head waves exhibit an anomalous phase shift, which is due probably to the finite thickness of the model materials. For the dispersive effect to be negligible, the thickness of the two‐dimensional model must be less than approximately one‐fifteenth of the wavelength of interest.
DIRECT INTERPRETATION OF TWO‐DIMENSIONAL STRUCTURAL FAULTS FROM GRAVITY DATA
Authors: Paul Mrinal K. , Datta Sukumar , Banerjee Buddhadeb
Published: October 2002

Some methods of direct determination of the parameters of a two‐dimensional structural fault with horizontal plane faces, from the gravity profile caused by it, have been formulated in this paper. The upward continuation of the two‐dimensional gravity profile plays an important role in these methods. The determinations by these methods are unique for structures of the same type in the sense that no structure of the same type other than that arrived at by the proposed methods can give rise to the observed anomaly. The necessary coefficients for upward continuation of two‐dimensional gravity data and the theory involved in their determinations form the appendix of this paper.
THE COEFFICIENT OF COHERENCE: ITS ESTIMATION AND USE IN GEOPHYSICAL DATA PROCESSING
Authors: Foster M. R. , Guinzy N. J.
Published: October 2002

The coefficient of coherence between two stationary time series was introduced by Wiener in 1930. It is related to the signal‐to‐noise ratio, to the minimum prediction error, and has important invariance properties. As an estimate of this parameter, most geophysicists have used the so‐called “sample coherence.” An approximate distribution of the sample coherence for Gaussian data has been derived by N. R. Goodman. We have tested this distribution by means of Monte Carlo experiments for validity and robustness (insensitivity to the Gaussian assumption). It has passed the tests. The Goodman distribution provides a means of constructing estimates of the true coherence which are better than the widely used sample coherence. It can also be used to calculate confidence intervals. Finally, it forms a basis for choosing the lag window and data window necessary for best estimation of the true coherence. For good estimates of the true coherence, two precautions must be observed: 1. The cross‐spectrum and power spectra of the two time series must be smoothly varying over the width of the spectral window. 2. The ratio of the length of the data window to the lag window must be large. For most seismic work the second requirement severely limits the spectral resolution. Examples show that large errors can result if this resolution is not sufficient to satisfy the first requirement. In many geophysical studies the parameter of interest is the signal‐to‐noise ratio. Because of its relation to the coherence, the Goodman distribution provides a basis for its estimation as well.
DEMAGNETIZATION EFFECT OF A RECTANGULAR PRISM
Authors: Sharma P. Vallabh
Published: October 2002

Demagnetization factors have so far been introduced and calculated only for bodies bounded by a second degree surface. For taking into account the demagnetization effect of a body of some other shape, such as a rectangular prism, the normal practice hitherto has been to approximate it by an ellipsoid of known demagnetization factor. As shown later, the demagnetization factors so obtained are, in general, subject to considerable errors excepting for some particular dimensional ratios.
THE CSM TEST AREA FOR ELECTRICAL SURVEYING METHODS
Authors: Harthill Norman
Published: October 2002

Testing of geophysical equipment and methods over a region of known geology has long been considered desirable if not actually necessary. It is the purpose of this note to bring to the attention of the geophysical community the development of a test area for the evaluation of electrical prospecting methods. The test area is a strip, 19 km broad and 280 km long, made up of the tiers of townships 1N and 2N stretching between R42W and R70W in eastern Colorado (Figure 1). Access to the strip is easy as the area is relatively level and county roads border most sections; population is sparse.
GEOLOGIC IMPLICATIONS OF AEROMAGNETIC DATA FOR THE EASTERN CONTINENTAL MARGIN OF THE UNITED STATES
Authors: Taylor Patrick T. , Zietz Isidore , Dennis Leonard S.
Published: October 2002

An aeromagnetic survey extending from the Gulf of Maine to the tip of Florida was conducted by the U. S. Naval Oceanographic Office between 1964 and 1966. Flight traverses were flown in a northwesterly direction at right angles to the geologic grain. The flight lines were approximately 800 km long and had an 8‐km separation. The survey traversed part of the New England, Piedmont, and Coastal Plain provinces and extended some 320 km beyond the continental shelf into the Atlantic Ocean. Despite the wide flight‐line spacing, numerous geological and structural features became apparent from this survey. Interpretation of these features was aided by using the available gravity and seismic data in addition to the State and Provincial geologic maps. The residual aeromagnetic map shows a continuous magnetic high on or near the continental slope as far south as the 31st parallel. At about the 36th parallel, this east‐coast magnetic anomaly splits into two branches, and both of them parallel the 850‐fathom contour. At the 31st parallel, the outer branch of the anomaly swings westward and crosses the coastline near Brunswick, Georgia. This continuous magnetic anomaly may result from an igneous intrusive body that parallels the edge of the pre‐Paleozoic continental landmass. These magnetic data suggest that Florida and part of Georgia were added to the paleo‐continent in pre‐Paleozoic time. Landward from the east‐coast anomaly, the magnetic field is quite variable, whereas oceanward it has an extremely small gradient. The absence of magnetic anomalies east of the continental slope suggests that in this region layer 2 may be composed of metamorphosed basalt. The characteristic magnetic patterns observed over the Piedmont and New England provinces extend oceanward to the east‐coast anomaly.
PHYSICAL PROPERTIES OF MARINE SEDIMENTS AS RELATED TO SEISMIC VELOCITIES
Authors: Morgan Nabil A.
Published: October 2002

An investigation of the dependence of seismic velocities on different physical properties of naturally occurring fresh‐water sediments in Lake Erie has been conducted. Cores from one lake bottom were collected and the longitudinal seismic wave velocities as well as the physical properties (grain density, bulk density, porosity, median diameter, and phi deviation) were measured. The data were fitted with a second‐order polynomial in all the physical properties to the seismic velocity. Independent variables were ranked according to their individual effect upon the sum of the squares of the regression residuals. A variance‐analysis table was set up, and the coefficients were tested by a series of F ratios at certain probabilities. As porosity and bulk density are linearly related, these were not included together in the same model. There are strong indications that the porosity and its square together with the median diameter play a significant role in determining the seismic velocity at the probability of 0.90. At the higher probability of 0.99, the median diameter proved insignificant. The cubic term of porosity is insignificant at the 0.50 level.
CONTOURING OF VLF‐EM DATA
Authors: Fraser D. C.
Published: October 2002

Prospecting for conductive deposits with ground VLF-EM instruments has received considerable impetus with the recent development of lightweight receivers. The large geologic noise component, which results from the relatively high‐transmitted frequency, has caused some critics to avoid use of the technique. Those who routinely perform surveys with a VLF-EM unit find that, in some areas, a 5‐degree peak‐to‐peak anomaly can be significant, whereas anomalies having amplitudes in excess of 100 degrees may occur as well. Consequently, there is a dynamic range problem when presenting the results as profiles plotted on a field map. A data manipulation procedure is described which transforms noisy noncontourable data into less noisy contourable data, thereby eliminating the dynamic range problem and reducing the noise problem. The manipulation is the result of the application of a difference operator to transform zero‐crossings into peaks, and a low‐pass smoothing operator to reduce noise. Experience has shown that field personnel can routinely perform the calculations which simply involve additions and subtractions.
SOME FORMULAS USEFUL IN THE INTERPRETATION OF GRAVITATIONAL AND MAGNETIC PROFILES
Authors: Milcoveanu D.
Published: October 2002

General formulas for the calculation of the gravimetric quantities g, [Formula: see text], [Formula: see text], and [Formula: see text] caused by two‐dimensional models bounded by certain analytical curves are presented. Model curves show anomalies in these gravimetric quantities for the case of circular segments. On the basis of the well‐known Poisson formula relating magnetic and gravimetric potentials, formulas are derived for the calculation of magnetic quantities produced by two‐dimensional models bounded by certain analytical curves. Examples illustrate the case where the analytical curve is an arc of circle. Model curves show anomalies in the magnetic quantities for circular segments. The model curves representing theoretical gravimentric and magnetic anomalies can be used for practical interpretation problems.
On: “Variations of Vertical Gravity Gradient in New York City and Alpine, New Jersey” by John T. Kuo, Mario Ottaviani, and Shri K. Singh (GEOPHYSICS, April 1969, p. 235–248).
Authors: Thyssen-Bornemisza Stephen
Published: October 2002

In their paper, Kuo et al, following the footsteps of Hammer (1938), reported interesting vertical gradient observations in high buildings with a gravity meter. However, conclusion (5) drawn by Kuo et al should be discussed briefly in order to avoid an incorrect impression.
THREE‐DIMENSIONAL SEISMIC MODELING
Authors: Hilterman Fred J.
Published: October 2002

Record sections from three‐dimensional acoustic models often contain diffracted events not predictable by classical raypath theory. Several observed and calculated record sections from models of typical geologic structures such as synclines, anticlines, and faults verify this diffraction phenomenon. A careful interpretation of the character and moveout of these diffracted events is required to delineate certain portions of the geologic structures. A far‐field approximation of the retarded potential equation is suitable for direct time‐domain evaluation and is used to synthesize the calculated sections. The excellent comparisons between the calculated and observed record sections suggest that the mathematical modeling technique can be a useful tool for enhancing field interpretations.
DEVELOPMENTS IN SEISMIC DATA PROCESSING AND ANALYSIS (1968–1970)
Authors: Schneider William A.
Published: October 2002

The subject matter of this review paper pertains to developments during the past several years in the area of reflection seismic data processing and analysis. While this subject area is extensive in both its breadth and scope, one indisputable fact emerges: the computer is now more pervasive than ever. Processing areas which were computer intensive, such as signal enhancement, are now even more so; and those formerly exclusive domains of man, such as seismic interpretation, are beginning to feel the encroachment of the large number crunchers. What the future holds is anyone’s guess, but it is quite probable that man and computer will share the throne if the interactive seismic processing systems on the drawing boards come to pass. For the present and recent past, however, the most intensively developed areas of seismic data processing and analysis include 1) computer extraction of processing parameters such as stacking velocity and statics, 2) automated detection and tracking of reflections in multidimensional parameter space to provide continuous estimates of traveltime, amplitude, moveout (velocity), dip, etc., 3) direct digital migration in two dimensions, giving improved subsurface “pictures” and utilizing diffraction energy normally lost by specular processing techniques, and 4) development of quantitative understanding of the limitations imposed by current seismic processing practice and assumptions with regard to structural and stratigraphic model building, and recognition of the ultimate need for an iterative signal processing—information extraction—model building closed loop system.
SEISMOGEOLOGIC EXPERIENCE IN THE BEAUFORT SEA
Authors: Hofer H. , Varga W.
Published: October 2002

Conventional seismic data processing was applied to 24‐fold airgun data acquired in the Liverpool and Mackenzie Bay areas of the Beaufort Sea. These data provided general indications of the regional geology and the types of structures present. A part of one line in each area was chosen on the basis of its geologic content and data quality for reprocessing through a velocity analysis package. The purpose was to establish velocity, particularly interval velocity, as the common ground between geology and the seismic section. The velocity package performs a continuous analysis for time and moveout as well as amplitude on all events present within a common‐depth‐point gather. Events are joined from depth point to depth point on the basis of similarity in time, moveout, amplitude, and polarity to yield a segment file. This file is statistically analyzed and sorted into two subsets, primary and nonprimary files, using segment velocity as the criterion. Interval velocities can be calculated between those segments that exhibit velocities characteristic of primary energy. The space‐variant velocity control derived from the data was used to correct it for moveout. A marked improvement in the interpretability of the data resulted on both lines. The data‐derived interval velocities give intriguing indications of lithology which can be correlated to acoustic logs on shore. Plausible hypotheses of offshore geology have been derived without the benefit of any offshore drilling.
RADIO INTERFEROMETRY DEPTH SOUNDING: PART I—THEORETICAL DISCUSSION
Authors: Annan A. P.
Published: October 2002

Radio interferometry is a technique for measuring in‐situ electrical properties and for detecting subsurface changes in electrical properties of geologic regions with very low electrical conductivity. Ice‐covered terrestrial regions and the lunar surface are typical environments where this method can be applied. The field strengths about a transmitting antenna placed on the surface of such an environment exhibit interference maxima and minima which are characteristic of the subsurface electrical properties. This paper (Part I) examines the theoretical wave nature of the electromagnetic fields about various types of dipole sources placed on the surface of a low‐loss dielectric half‐space and two‐layer earth. Approximate expressions for the fields have been found using both normal mode analysis and the saddle‐point method of integration. The solutions yield a number of important results for the radio interferometry depth‐sounding method. The half‐space solutions show that the interface modifies the directionality of the antenna. In addition, a regular interference pattern is present in the surface fields about the source. The introduction of a subsurface boundary modifies the surface fields with the interference pattern showing a wide range of possible behaviors. These theoretical results provide a basis for interpreting the experimental results described in Part II.