Showing papers by "University of Arizona published in 1969"
TL;DR: A relatively simple numerical model of the energy balance of the earth-atmosphere is set up and applied in this paper, where the major conclusions of the analysis are that removing the arctic ice cap would increase annual average polar temperatures by no more than 7C, that a decrease of the solar constant by 2-5% might be sufficient to initiate another ice age, and that man's increasing industrial activities may eventually lead to a global climate much warmer than today.
Abstract: A relatively simple numerical model of the energy balance of the earth-atmosphere is set up and applied. The dependent variable is the average annual sea level temperature in 10° latitude belts. This is expressed basically as a function of the solar constant, the planetary albedo, the transparency of the atmosphere to infrared radiation, and the turbulent exchange coefficients for the atmosphere and the oceans. The major conclusions of the analysis are that removing the arctic ice cap would increase annual average polar temperatures by no more than 7C, that a decrease of the solar constant by 2–5% might be sufficient to initiate another ice age, and that man's increasing industrial activities may eventually lead to a global climate much warmer than today.
996 citations
TL;DR: In this article, the inadequacy of previous calculations of terminal velocities at other than sea level conditions is discussed, and empirical formulae are presented which fit the data very closely.
Abstract: The inadequacy of previous calculations of terminal velocities at other than sea level conditions is discussed. Attention is called to actual measurements of terminal velocities at different air densities, and empirical formulae are presented which fit the data very closely.
373 citations
TL;DR: In this paper, mass distributions of fragmented rocks are analyzed for the purpose of interpreting extraterrestrial rock samples, which can be used to interpret extraterrestrial meteorites or meteorites from repeated and/or hypervelocity collisions.
282 citations
TL;DR: Strong light flashes have been detected from the fast pulsar in the Crab Nebula.
Abstract: Strong light flashes have been detected from the fast pulsar in the Crab Nebula.
173 citations
TL;DR: Evidence is presented that the intracellular level of cyclic 3', 5'-AMP within melanophores may be responsible for the regulation of movement of melanin granules.
Abstract: SYNOPSIS. The physiological regulation of color changes in reptiles as studied in the lizard, Anolis carolinensis , is discussed. In Anolis , the ability to adapt to a background is dependent upon the level of circulating MSH, therelease of which is dependent on information received through the eyes. Blinded (or intact) lizards are brown under conditions of strong illumination and green under conditions of lower light intensities, and, again, these color changes are regulated by MSH. According to Kleinholz, color changes in the blinded lizard are regulated by dermal photoreceptors. High or low temperatures directly affect the color of Anolis skins and alter the rate at which skins respond to hormones. Aggregationof melanin granules within Anolis melanophores in response to sympathomimetic stimulation is regulated through alpha adrenergic receptors whereas dispersion of melanin granules in response to such stimulation is controlled through beta adrenergicreceptors possessed by the melanophores. Most Anolis melanophores possess both alpha and beta adrenergic receptors, but some melanophores possess only beta adrenergic receptors. In the normal physiology of the lizard, under conditions of stress, stimulation of alpha adrenergic receptors by catecholamines leads to an “excitement—pallor“followed by an “excitement—darkening“ resulting from stimulation of beta adrenergic receptors which causes dispersion of melanin granules within localized populations of melanophores. Thus, in Anolis , dispersion of melanin granules within melanophores is regulated by both MSH and by catecholamines. Evidence is presented that the intracellular level of cyclic 3', 5'-AMP within melanophores may be responsible for the regulation of movement of melanin granules.
123 citations
TL;DR: Except for reported differences in diameters, the findings on fine structure of microtubules (MT) involved in mitosis and meiosis are consistent throughout the literature.
Abstract: Except for reported differences in diameters, the findings on fine structure of microtubules (MT) involved in mitosis and meiosis are consistent throughout the literature. Whatever the sources of cells for study, plant (14, 10, 17, 6) or animal (14, 9, 13, 20), no deviations have turned up, other than in centrioles which have tubules arrayed in triplets. Exceptions to the MT structure of the mitotic and meiotic apparatus are found in those tubules associated with cilia and flagella (2, 1). Certain of these, the peripheral tubules, commonly exist in pairs with additional structures-arms-attached to one tubule of the pair. The two central tubules
85 citations
TL;DR: Differential stress-strain relationships are used to generate a system of simultaneous firstorder differential force-displacement equations which are integrated numerically to obtain the stresses, strains, and displacements in inelastic structures.
Abstract: Differential stress-strain relationships are used to generate a system of simultaneous firstorder differential force-displacement equations which are integrated numerically to obtain the stresses, strains, and displacements in inelastic structures. For the biaxially stressed element, the concept of isotropic hardening and a generalized stress are used to evaluate an effective modulus and Poisson's ratio, which vary continuously from their initial values during elastic straining action to their asymptotic values during intense plastic straining action. The surface of plasticity for this element closely approximates the von Mises surface when the generalized stress is set equal to the von Mises stress and the strain distribution is essentially identical to that obtained by the Prandtl-Reuss incremental flow theory. The analysis of the MIT shear lag structure is presented to demonstrate the applicability of the method to systems of practical size and interest. Nomenclature A = equilibrium matrix B = compatibility matrix C = stress-strain matrix C = differential stress matrix E = Young's modulus Et = tangent modulus Es = secant modulus K — stiffness matrix K = differential stiffness matrix P = applied load parameter u = element nodal displacements X = element nodal forces X = load constant n = Poisson's ratio fjLt = tangent Poisson's. ratio Us = secant Poisson's ratio e = strain a- = normal stress
83 citations
TL;DR: Bristlecone pines (Pinus aristata Engelm) have been found to attain ages over 4,000 years in the White Mountains of the United States as discussed by the authors.
Abstract: Bristlecone pines (Pinus aristata Engelm.) locally attain ages over 4,000 years. In the White Mountains, California, old trees are widely distributed near the lower forest border, but are restricted to exposed, rocky areas at higher altitudes. Comparative aridity seems to be an important feature of the "old—age" habitat. Occurrences of older (1,5000—4,900 years) bristlecone pines in the moister mountain ranges of Nevade and Utah are analogous to those at higher altitudes in the White Mountains, suggesting that local edaphic and physiographic factors can offset the effects of a regional precipitation gradient. Attainment of an age greater that about 1,500 years apparently depends on the adoption of a strip—growth habit, which permits the aging bristlecone pine to maintain a nearly constant ratio of green to non—green tissue. Slow growth rates, wind damage, and soil erosion may be conducive to cambial area reduction. Other features of old—age stands, such as the wide spacing of the trees, the compactness of...
83 citations
TL;DR: As predicted, experimental subjects improved significantly, relative to controls, on both outcome measures; as further expected, the experimental variations did not produce significantly different outcomes among treatment conditions.
81 citations
TL;DR: Three different allelic isozyme systems were analyzed in population samples of a species of ant from Texas, and correlation found between patterns of variability in the enzyme systems themselves was consistent with the hypothesis that all three enzyme systems were affected by the environmental factors.
Abstract: Three different allelic isozyme systems (two esterases, ESH and ESR, and a malic dehydrogenase, MDH) were analyzed in population samples of a species of ant, Pogonomyrmex barbatus, from Texas Allelic frequencies were determined for several collection localities, and a number of significant differences were found Principal component analysis was used to compare the patterns of variability of the allelic frequencies with environmental factors Significant correlation was particularly evident with respect to weather and the pattern of variability in both esterases, and it is therefore suspected that natural selection is important in determining the allele frequency patterns Observed and expected genotypic proportions were found in good agreement, generally, but in some localities homozygotes appeared in significantly greater numbers than expected Heterotic selective maintenance was thus not indicated Correlation found between patterns of variability in the enzyme systems themselves was consistent with the hypothesis that all three enzyme systems were affected by the environmental factors
67 citations
TL;DR: The depolymerization of lignin by wood-rotting fungi may result from a series of one-electron steps catalyzed by phenol oxidases, and a biological clock mechanism appeared to mediate these reactions.
TL;DR: Granular gland secretion in response to catecholamines is apparently mediated by muscle contraction resulting from α-adrenergic stimulation.
TL;DR: Early Precambrian Onverwacht microstructures studied in petrographic thin sections and powdered preparations for possibility of oldest terrestrial fossils were used in this article for finding the earliest terrestrial fossils.
Abstract: Early Precambrian Onverwacht microstructures studied in petrographic thin sections and powdered preparations for possibility of oldest terrestrial fossils
TL;DR: In this article, the point amplitude response of a diffraction-limited pupil with a magnified aperture of 1/Δ times the given pupil aperture was shown to approximate low contrast cosine fringes over its central region, with a frequency and amplitude that rapidly accelerate as the aperture edge is approached.
Abstract: In theory, an optical system with a finite aperture can be coated to produce arbitrarily perfect imagery over a limited field. When the object is of limited extent, this field can be made the optical conjugate to the object, so that the whole object is imaged with arbitrary precision. The required pupil coating approximates low-contrast cosine fringes over its central region, with a frequency and amplitude that rapidly accelerate as the aperture edge is approached. Here the maximum occurs as a narrow spike. The frequency near the central region varies directly with the total extent of the conjugate field, and inversely with the required central core width Δ in the point amplitude response. As Δ is made arbitrarily narrow, the point amplitude response approaches the form of a sinc function over the field of view. This function is precisely the point amplitude for a diffraction-limited pupil with a magnified aperture of 1/Δ times the given pupil aperture ! The only image property that is not in compliance w...
TL;DR: In this paper, the authors provided digestible energy levels of 115% (low-prepartum) and 160% (high-pre partum) of maintenance requirements for groups of 32 Holstein cows during the last six to eight weeks of gestation.
TL;DR: In this article, the effect of pressure up to 6 kbar on the electrical resistance quenched into gold and aluminum at various linear quench rates has been measured, and formation volumes of 6.4 and 6.15 µmole, respectively, are inferred.
Abstract: The effect of pressures up to 6 kbar on the electrical resistance quenched into gold and aluminum at various linear quench rates has been measured. Formation volumes of 6.8\ifmmode\pm\else\textpm\fi{}0.4 and 6.38\ifmmode\pm\else\textpm\fi{}0.15 ${\mathrm{cm}}^{3}$/mole, respectively, are inferred. Agreement with earlier measurements in gold is good when they are corrected for the pressure coefficient of resistance. The value for aluminum supports earlier values obtained by other techniques. There is also evidence that dislocations are not sinks for the majority of the vacancies during the quench.
TL;DR: It is proposed that iridophores of these species undergo a morphological color response without an accompanied physiological color response.
TL;DR: Binary encounter model for ionization by charged particle impact modified to evaluate cross section for ionisation of positive ions by electron impact as discussed by the authors, where the cross section is defined by a binary encounter model.
Abstract: Binary encounter model for ionization by charged particle impact modified to evaluate cross section for ionization of positive ions by electron impact
TL;DR: In this article, the authors proposed a solution for low Reynolds number turbulent gas flow based on Reynolds number dependent velocity profile, and solved the thermal entry problem for turbulent gas flows based on the velocity profile.
Abstract: Thermal entry problem solution for low Reynolds number turbulent gas flow based on Reynolds number dependent velocity profile
TL;DR: The analytical ultracentrifuge has been employed as a primary tool for the study of this heterogeneity among lipoproteins, and the value of this technique becomes clear when writing the equation relating the sedimentation coefficient to other macromolecular parameters.
Abstract: Human lipoproteins are often divided into three main groups: the high-density lipoproteins, the low-density lipoproteins and the chylomicra. The high-density lipoproteins are further subdivided into two classes, HDLz and HDL3. The lowdensity lipoporteins are also subdivided into two classes, the low-density, Sr 0-20, and the very-low-density, Sf 20-400, lipoproteins (Scanu, 1965). Where are these lipoproteins manufactured and what physiological roles do they play? The chylomicra are formed in the intestine, and they function in transporting alimentary lipids from the intestines to the tissues. The very-low-density lipoproteins are manufactured principally in the liver, and apparently supply neutral fats synthesized by the liver to other tissues and storage depots. The highdensity lipoproteins also are manufactured by the liver. Some evidence indicates that these may serve to facilitate the exodus of lipids from the plasma and to keep the tissues free from unwanted lipid deposits (Fredrickson, Levy, and Lees, 1967). Lipoproteins are unique among biological macromolecules in that they are not polymers, for the most part. By and large, the lipid moiety is held in place by noncovalent bonds. And the lipoproteins may grow or shrink depending upon the availability and chemical potential of environmental lipids. Thus, a heterogeneity in size, density, and molecular weight is expected to exist among these molecules, and it is found (Nichols, 1967). The analytical ultracentrifuge has been employed as a primary tool for the study of this heterogeneity. The value of this technique becomes clear when writing the equation relating the sedimentation coefficient to other macromolecular parameters:
TL;DR: In this article, the authors examined differential cross sections for production of secondary electrons in the ionization of atoms by charged-particle impact in the classical binary-encounter approximation.
Abstract: Differential cross sections for production of secondary electrons in the ionization of atoms by charged-particle impact are examined in the classical binary-encounter approximation. General scalable expressions are given for both electron and heavy-charged-particle impact, and are compared with experimental and quantum treatments where possible. It is found that this formulation provides simple physical explanations of most features of ejected electron energy and velocity distributions. Proton-impact results are found to be in excellent agreement with experiment, and the electron-impact results converge to the Born results as expected.
TL;DR: In southern Arizona, young pallid bats are bom in mid-June, and the average juvenile has reached the adult range of forearm size by the fifth week of age, and almost all are within adult range by the seventh week.
Abstract: In southern Arizona, young pallid bats are bom in mid-June. the average juvenile has reached the adult range of forearm size by the fifth week of age, and almost all are within adult range by the seventh week. the body weights of the young of both sexes, however, are significantly less than those of the adults until after autumn of the first year, and yearling females weigh significantly less than adults through the autumn of their second year. Development of young pallid bats in wild populations apparently proceeds through several stages at a faster rate than that of young bats reared in captivity. Forearm measurement provides a usable means of estimating ages of the younger bats. by the combined use of forearm measurement and observation of certain developmental stage “check points,” rough estimates of age can be made at least until adult conditions are reached. the use of a checklist of features allows the young of the year to be distinguished from the adults through late fall of the first year. Pallid bats show no sexual dimorphism in forearm lengths, and the young show none in body weight until about the end of the first year of age. Yearling females normally give birth to only one young, whereas most older females give birth to two. Young males are not sexually active in their first autumn and probably not during their first year. Adult females nurse only the young to which they have given birth.
TL;DR: On the basis of NMR, mass, and IR spectrometry, the structure of a new lignan, 3-(3,4-methylenedioxybenzyl)-4-(3“,4”,5-trimethoxybenZyl) tetrahydrofuran (named burseran), is proposed.
TL;DR: A cytological analysis of the in vitro response of frog skin chromatophores to hormonal and pharmacological agents is presented and the significance of the diverse chromatophile responses to stimulation is discussed in light of interpretations that might erroneously be drawn from objective photometric measurements as in the frog skin bioassay.
Abstract: A cytological analysis of the in vitro response of frog skin chromatophores to hormonal and pharmacological agents is presented. The significance of the diverse chromatophore responses to stimulation is discussed in light of interpretations that might erroneously be drawn from objective photometric measurements as in the frog skin bioassay. Melanophorestimulating hormone (MSH) disperses melanin granules within both dermal and epidermal melanophores; the previously dispersed reflecting platelets within iridophores become aggregated. Acetylcholine lightens MSH-darkened skin to a near pre-MSH level by reversing the action of MSH on all chromatophores. Melatonin and norepinephrine only weakly reverse the darkening action of MSH on frog skin as not all chromatophores respond to these agents. Melatonin causes melanin granule aggregation within only a small number of localized dermal melanophores and is without effect on iridophores. Norepinephrine, unlike melatonin, but like acetylcholine, redisperses the refle...
TL;DR: The high-salt flotation technique for lowdensity lipoproteins and the calculation of molecular weights from such data is described, which can virtually eliminate the uncertainty in calculated molecular weight for a given uncertainty in lipoprotein density.
TL;DR: The data suggest that stimulation of the beta adrenergic receptor of Scaphiopus couchi melanophores results in an intracellular increase in cyclic AMP which then initiates melanin granule dispersion, which suggests that skin darkening is possibly mediated by cyclicAMP.