Showing papers by "University of Iowa published in 1971"

Plasma in the Earth's polar magnetosphere

Abstract: First observations of the plasmas in the dayside polar magnetosphere were obtained with the earth-satellite Imp 5 during July-August 1969. Several of the more important observational results are the following. (1) The polar neutral ‘points’ that appear at the high-latitude magnetopause in mathematical models for the shape of the geomagnetic cavity formed by the interaction of the solar wind with the geomagnetic field are observationally ‘bands’ with width ∼1 RE across the dayside high-latitude magnetopause (one band in the northern hemisphere and presumably a second in the southern hemisphere). (2) These two bands, or regions of the magnetopause through which the magnetosheath plasma has direct access to the magnetosphere, and the corresponding extension of these bands from magnetopause to auroral altitudes have been designated herein as the ‘polar cusps.’ (3) At all other positions of the dayside magnetopause, the magnetopause appears to be an effective barrier against the direct entry of magnetosheath plasma. (4) During periods of relative magnetic quiescence the intersection of the dayside polar cusp with the auroral zone is positioned at invariant latitude Λ=79° (±1°) and its latitudinal width is 20 to 400 km projected onto the auroral zone. (5) During periods of the relative magnetic disturbance the position of the polar cusp moves equatorward by several degrees in invariant latitude without a large increase in its latitudinal width, i.e., by factors ≲2. (6) The high-latitude termination of energetic trapped electron (E>45 kev) intensities in the high-latitude dayside outer radiation zone occurs coincident with the polar cusp, albeit these intensities are small and of irregular profile with radial distance in this region. (7) No measurable intensities of energetic electrons (E>40 kev), magnetosheath protons and electrons, and ring-current protons were observed at latitudes above the polar cusp, i.e., in the polar cap region. (8) The proton and electron differential energy spectrums as viewed in the solar direction in the distant polar cusp (within several earth radii of the magnetopause) are identical to those observed within the magnetosheath to within observational accuracy. (9) The bulk velocity of protons in the distant polar cusp as deduced from the angular distributions appears to be lower than that of the magnetosheath plasma near the magnetopause by factors ∼2 or 3. (10) In the midaltitude polar cusp at ∼4 to 5 RE geocentric radial distances, the proton spectrum differs from that at the magnetosheath in that protons with energies ≲500 ev are severely less than those observed in the magnetosheath. (11) The proton spectrums in the midaltitude polar cusp are similar to those in the distant plasma sheet with the exception that the proton number densities in the polar cusp are typically larger by factors ∼20 to 200. (12) The angular distributions of proton intensities in the midaltitude polar cusp are strongly peaked along the local magnetic field (i.e., down into the auroral zone); the dimensions of the atmospheric loss cone at these altitudes appear to be insufficiently large to account for the observed anisotropy; and (13) the magnetosheath plasma in the midaltitude polar cusp is observed to be separated into two thin sheets, one of magnetosheath proton intensities and the other populated with magnetosheath electrons; these sheets are immediately adjacent to each other with the electron sheet equatorward of the proton sheet; their latitudinal widths as projected into the auroral zone are roughly equal, ∼10 to 200 km. These observations, along with recent measurements from other earth satellites, have been interpreted in terms of a proposed magnetospheric model with several new features, among which are the following. (1) Plasma sheet protons gain access to the magnetospheric field lines via the dayside polar cusps. (2) All magnetic field lines threading the distant plasma sheet beyond ∼20 or 30 RE were convected from the polar cusps. (3) Magnetic field lines in the polar cap region of the magnetotail do not merge or pass through the plasma sheet.

Effects of Urban Spatial Structure on Individual Behavior

Abstract: (1971). Effects of Urban Spatial Structure on Individual Behavior. Economic Geography: Vol. 47, PERSPECTIVES ON URBAN SPATIAL SYSTEMS, pp. 36-48.

An Evaluation of 55 Cobalt Substituted Nitinol Wire for Use in Orthodontics

Abstract: The authors suggest that 55 cobalt substituted Nitinol wire be used in orthodontics by reason of its properties of elasticity and resistance to corrosion. The Nitinol wires are compared with single strand stainless steel and triple strand Twistflex wires.

Influence of physical activity on ligament insertions in the knees of dogs.

Abstract: 1. At ligament-bone junctions in dogs existing at varying levels of physical activity, strength diminished as activity diminished. 2. At the proximal end of the tibia, subperiosteal resorption weakened the ligament-bone junction of the medical collateral ligament. A similar change was seen in the fibular attachment of the lateral collateral ligament but not in the other ligament attachments about the knee. 3. Microscopically, widespread subperiosteal bone resorption developed in inactive dogs. 4. Simple caging for six weeks or more produed boen resorption. 5. With continued caging, bone resorption at the ligament-bone attachment healed over a period of six months or more as fibrous tissue replaced resorbed bone and then became mineralized. The widespread subperiosteal bone loss consequent to inactivity probably healed in the same way, suggesting on the basis of this histological evidence that inactivity produces bone resorption which is followed by bone accretion.

The Study of Organizational Effectiveness

Abstract: This paper reviews the goal approach and the system resource approach to the study of organizational effectiveness. First, the goal approach is defended with respect to criticisms made by the users of the system resource approach. Next it is criticized for its failure to develop general measures of effectiveness. The system resource approach is then criticized because optimization is not measured, few general measures are used, and the basic rule of mutual exclusiveness is seriously violated. Finally, a general measure of effectiveness is suggested, based on Georgopoulos and Mann's (1962) study of community general hospitals.

Cournot Oligopoly and Competitive Behaviour

Abstract: This paper shows that the Cournot oligopoly model need not converge to perfect competition, regardless of the quasi-competitiveness of the model. Convergence takes place if, and only if, there are no scale economies. Without convergence, interest centres on the other properties of the Cournot model! It is shown, for example, that both quasicompetitiveness and stability may break down with large numbers of firms. But an example suggests that the numbers involved, though not impossible, might be higher than one could expect in practice. Throughout the analysis we examine the strong case in which all firms are identical. This strips away the non-essentials and considerably simplifies the analysis. Section II describes the model and demonstrates the uniqueness of the solution. Section III is devoted to the limiting behaviour of the Cournot model. Section IV examines the quasi-competitiveness and stability of the model. Section V offers an illustrative and suggestive example based on a general linear demand function and a general cubic cost function. Finally, Section VI makes some concluding remarks on the relation between numbers of firms and competitive behaviour.

Utilization of aliphatic hydrocarbons by micro-organisms.

Abstract: Publisher Summary This chapter describes utilization of aliphatic hydrocarbons by microorganisms and discusses certain aspects of the oxidation and assimilation of the simple aliphatic alkanes and alk-l-enes for the most part microbial. The number of bacteria recorded as being “hydrocarbon-oxidizers” exceeded the number of yeasts and filamentous fungi. The greater propensity for oxidation of aliphatic hydrocarbons by bacteria was more apparent than real because it reflected the lack of investigations using yeasts and filamentous fungi. The chapter reviews the information on the kinds of yeasts and molds implicated in aliphatic hydrocarbon oxidations and reviews reports on the catabolism of hydrocarbons by these two groups. The genera of yeasts reported to assimilate n-alkanes,alk-1-enes, and genera of filamentous fungi utilize aliphatic hydrocarbons for growth are enlisted. Certain ecological principles with reference to microorganisms utilizing hydrocarbons have been applied to the prospecting for petroleum. Lower vapor pressures of the n-alkanes at the lower temperature indicated that physical characteristics of the hydrocarbon as well as the metabolic potentials of the organism must be considered in assessing the utilizability of hydrocarbons as carbon sources for growth. Many micro-orgmisms like bacteria, which utilize the long-chain hydrocarbons to the exclusion of the shorter members of a series find that these shorter members are “toxic” because of their greater solubility and therefore their higher concentration. Yeasts and filamentous fungi readily utilize long-chain rather than short-chain hydrocarbons. Filamentous fungi contain members that utilize short chitin hydrocarbons for growth.

Characteristics of soft solar X-ray bursts

Abstract: The burst component of the solar X-ray flux in the soft wavelength range 2 < λ < 12 A observed from Explorer 33 and Explorer 35 from July 1966 to September 1968 was analyzed. In this period 4028 burst peaks were identified.

Distributions of plasmas and electric fields over the auroral zones and polar caps

Abstract: Low energy particle plasma sheet and convection electric field distributions over auroral zones and polar caps from satellite Injun 5 observation

Physiological responses of frog vestibular fibers to horizontal angular rotation.

Abstract: 1. Single neuronal discharges in frog's vestibular nerve were recorded in unanesthetized preparations with glass microelectrodes. The nerve fibers supplying the horizontal semicircular canal are divided into two types according to the characteristics of their frequency responses to natural stimulation of the horizontal canal. The afferent fibers increase their firing rate only on ipsilateral rotation and cease to fire on contralateral acceleration. The efferent fibers usually increase their frequencies on rotation in either direction or show an increase in firing on contralateral rotation only. The thresholds of efferent fibers are generally higher as compared to afferent fibers. In addition, most of them show multisensory convergence. 2. Of the afferent fibers 65% showed frequency adaptation in response to prolonged acceleration steps whereas 35% did not show any sign of frequency decrease on prolonged stimulation. 3. Thirty out of 49 afferent units showed a non-linear relation between frequency increase and angular acceleration; in 19 units an approximately linear relationship was noted. In both types of responses the thresholds for frequency increase were in the range between 0.3–2.5°/sec2. 4. The time constants of the majority of fibers measured in the linear range were about 3 sec with a range between 1 and 10 sec. It is suggested that fibers having short time constants to acceleration and velocity step input represent acceleration-sensitive units whereas those having long time constants monitor angular velocity. Apparent ‘time constants’ were adopted for the non-linear range of non-linear units. These values decreased as the acceleration rate increased. 5. An approach to vestibular modeling, based on the present experimental results, is described in the Appendix.

Nonencapsulated Variant of Cryptococcus neoformans I. Virulence Studies and Characterization of Soluble Polysaccharide

Abstract: A weakly virulent nonencapsulated variant of Cryptococcus neoformans is described. The chemical structure and antigenicity of the soluble polysaccharides produced by the variant strain and a typical virulent strain were compared. The soluble polysaccharides produced by both strains were composed of the same constituent monosaccharides; however, the virulent strain produced a polysaccharide having a greater uronic acid content and a larger molecular size than that of the variant strain. Soluble polysaccharides from the two strains are not closely related immunologically. Soluble polysaccharide obtained from the virulent strain did not affect persistence of the variant strain in mice.

The quadratic problem for systems with time delays

Abstract: The theory of optimal control for time delay systems and the quadratic performance criterion is presented from two points of view: 1) the geometric approach, which yields a maximum principle, and 2) the dynamic programming-Caratheodory approach, which yields a feedback controller synthesis. The relationship of the two approaches is discussed, as well as extensions of the theory to non-linear problems and nonlinear performance criterion.

Responses of coronary vessels to adrenergic stimuli

Abstract: Experiments were done on anesthetized dogs (chloralose-urethane) to characterize the pattern of responsisveness to adrenergic stimuli. The left circumfles coronary artery was perfused with blood at constant rate. Changes in perfusion pressure of the coronary vessels reflected changes in coronary vascular resistance. Responses to direct electrical nerve stimulation of the cardiac sympathetic nerves, to intra-coronary injections of norepinephrine, isoproterenol, epinephrine; to electrical stimulation of carotid sinus nerves; and to stimulation of carotid chemoreceptors with nicotine and cyanide were tested. The intravenous administration of Practolol (1–2 mg/kg) eliminated changes in contractility which could result from these interventions and thus minimized or eliminated changes in coronary vascular resistance in response to changes in myocardial metabolism. The results indicated that 1) there is a paucity of alpha adrenergic vasoconstrictor receptors in the coronary vessels as compared to other vascular beds; 2) the coronary vascular beta receptors are not homologous to the cardiac beta receptors and are responsive to isoproterenol and epinephrine but not to norepinephrine nor to mose sympathetic nerve stimulation; 3) most of the dilator effect of isoproterenol represents activation of coronary and not cardiac beta receptors; 4) stimulation of baroreceptor nerves causes withdrawal of the sympathetic vasoconstrictor influence and minimal activation of cholinergic vagal vasodilator fibers; and 5) stimulation of chemoreceptors caused significant activation of cholinergic vagal vasodilator fibers.

Food consumption and growth of normal infants fed milk-based formulas.

Abstract: 154 formula-fed infants aged 8 to 112 days (69 males 89 females) were studied during the period January 1966 to April 1970 in order to collect normative data that would be useful for at least 3 purposes: 1) evaluation of other formulas providing 67 kcal/100 ml 2) study of factors affecting food consumption of normal infants and 3) assessment of performance of individual infants suspected of abnormality. Weight of each food consumed by each infant every day was recorded. Volume of intake and caloric intake were determined for each of the following age intervals: 8-13 14-27 28-41 42-55 56-83 and 84-111 days. Body weight and length of each infant were also measured at ages 8 14 28 42 56 84 and 112 days. Data analysis is based on 142 infants for whom complete data were available. 9 formulas were fed to the infants; each supplied 67 kcal/100 ml with protein from cows milk and fat from vegetable oils. Analysis of variance on a sex-specific basis for the age interval 8-111 days showed no statistical signficance (p<0.05) in feeding-related differences with respect to volume of intake caloric intake gain in weight or gain in length. At a specified body weight mean caloric intake was found to be greater among the younger than among older infants. During the interval 8-111 days mean values for males were greater than those for females with respect to the following: volume of intake calorie intake gain in weight and gain in length and gain in weight per unit of gain in length; these sex-related differences were statistically significant at p<0.05. Sex-related differences in gain in weight/unit of caloric intake or gain in length/unit of caloric intake were not statistically significant. The 10th 25th 50th 75th and 90th percentile values for gain in weight are presented for each sex for all age intervals and the same percentile values for gain in length for all age intervals of at least 34 days duration. Regressions of volume of intake on body weight caloric intake on body weight and weight gain are also presented for the various age groups. This study provides a basis for speculating about the partition of calories for growth and maintenance. An estimated 1/3 of caloric intake is utilized for growth during the age interval 8-111 days.

Traumatic dislocation of the long-finger extensor tendon. A clinical, anatomical, and biomechanical study.

Abstract: Five cases of traumatic dislocation of the extensor tendon of the long finger are presented. The anatomical defect consists of loss of continuity between the radial intrinsic muscles and the extensor tendon. The extensor tendon of the long finger sits on top of the proximal portion of the transverse fibers where it is maintained by a relatively poor fibrous attachment. The force tending to displace the normally situated extensor ulnarward is greatest in full extension, decreases during the first 60 degrees of flexion, and subsequently increases as flexion increases from 60 to 90 degrees. The force required to prevent further ulnar dislocation is large once the tendon is displaced. Simple primary repair is usually satisfactory for traumatic dislocation of the extensor tendon.

Historico-critical review of dimensional analysis

Abstract: The history of dimensional analysis is examined critically from the first notions about dimensions in old civilizations to the powerful methods of recent times. Dimensional analysis, as we know it and use it today, has been in active use for almost a century, although the basic ideas were published one hundred and fifty years ago. The elementary notions have a much longer history, because some of them were tacitly applied whenever a system of measurement of physical quantities was invented or put to use. This aspect has been keenly analyzed in the early 1920's by P.W. Bridgman, who used it in establishing one of the two basic theorems of dimensional analysis. The other theorem had been derived some thirty years before by A. Vaschy, and was rediscovered once or twice, and given more rigorous proofs by several mathematicians. Dimensional analysis remains a method which is most useful in areas in which knowledge is developing through an intermediate stage at which the basic laws are already known, but there is still a lack of powerful methods of solution. This study has been restricted to dimensional analysis proper, leaving out as much as possible the akin topics of similitude, modeling and simulation. Some rather recent developments of dimensional analysis have not been examined because of the obvious reason of their lack of historical prospective.