Showing papers by "Michigan Technological University published in 1990"

Codon Usage in Higher Plants, Green Algae, and Cyanobacteria

Abstract: Codon usage is the selective and nonrandom use of synonymous codons by an organism to encode the amino acids in the genes for its proteins. During the last few years, a large number of plant genes have been cloned and sequenced, which now permits a meaningful comparison of codon usage in higher plants, algae, and cyanobacteria. For the nuclear and organellar genes of these organisms, a small set of preferred codons are used for encoding proteins. Codon usage is different for each genome type with the variation mainly occurring in choices between codons ending in cytidine (C) or guanosine (G) versus those ending in adenosine (A) or uridine (U). For organellar genomes, chloroplastic and mitochrondrial proteins are encoded mainly with codons ending in A or U. In most cyanobacteria and the nuclei of green algae, proteins are encoded preferentially with codons ending in C or G. Although only a few nuclear genes of higher plants have been sequenced, a clear distinction between Magnoliopsida (dicot) and Liliopsida (monocot) codon usage is evident. Dicot genes use a set of 44 preferred codons with a slight preference for codons ending in A or U. Monocot codon usage is more restricted with an average of 38 codons preferred, which are predominantly those ending in C or G. But two classes of genes can be recognized in monocots. One set of monocot genes uses codons similar to those in dicots, while the other genes are highly biased toward codons ending in C or G with a pattern similar to nuclear genes of green algae. Codon usage is discussed in relation to evolution of plants and prospects for intergenic transfer of particular genes.

A space-efficient algorithm for local similarities.

Abstract: Existing dynamic-programming algorithms for identifying similar regions of two sequences require time and space proportional to the product of the sequence lengths. Often this space requirement is more limiting than the time requirement. We describe a dynamic-programming local-similarity algorithm that needs only space proportional to the sum of the sequence lengths. The method can also find repeats within a single long sequence. To illustrate the algorithm's potential, we discuss comparison of a 73,360 nucleotide sequence containing the human beta-like globin gene cluster and a corresponding 44,594 nucleotide sequence for rabbit, a problem well beyond the capabilities of other dynamic-programming software.

New cubic phases formed by alloying Al3Ti with Mn and Cr

Abstract: It has been found that Mn or Cr can substitute for Al in Al 3 Ti and change the crystal structure from tetragonal DO 22 to cubic L1 2 . The new phases have been produced with negligible porosity and second phases, and have compositions near Al 67 Mn 8 Ti 25 and Al 67 Cr 8 Ti 25 . As with other cubic forms of Al 3 Ti, the ternary addition can range from bout 5 to 15 at. pct. while still maintaining the cubic phase. These new cubic phases have significantly reduced hardnesses and greatly improved crack resistance compared to binary Al 3 Ti, as well as other cubic forms based on alloying with Fe, Ni, or Cu. In addition to appreciable ductility in compression, the new phases show some tensile ductility

Evaluation of gases, condensates, and SO2 emissions from Augustine volcano, Alaska: the degassing of a Cl-rich volcanic system

Abstract: After the March–April 1986 explosive eruption a comprehensive gas study at Augustine was undertaken in the summers of 1986 and 1987. Airborne COSPEC measurements indicate that passive SO2 emission rates declined exponentially during this period from 380±45 metric tons/day (T/D) on 7/24/86 to 27±6 T/D on 8/24/87. These data are consistent with the hypothesis that the Augustine magma reservoir has become more degassed as volcanic activity decreased after the spring 1986 eruption. Gas samples collected in 1987 from an 870°C fumarole on the andesitic lava dome show various degrees of disequilibrium due to oxidation of reduced gas species and condensation (and loss) of H2O in the intake tube of the sampling apparatus. Thermochemical restoration of the data permits removal of these effects to infer an equilibrium composition of the gases. Although not conclusive, this restoration is consistent with the idea that the gases were in equilibrium at 870°C with an oxygen fugacity near the Ni−NiO buffer. These restored gas compositions show that, relative to other convergent plate volcanoes, the Augustine gases are very HCl rich (5.3–6.0 mol% HCl), S rich (7.1 mol% total S), and H2O poor (83.9–84.8 mol% H2O). Values of δD and δ18O suggest that the H2O in the dome gases is a mixture of primary magmatic water (PMW) and local seawater. Part of the Cl in the Augustine volcanic gases probably comes from this shallow seawater source. Additional Cl may come from subducted oceanic crust because data by Johnston (1978) show that Cl-rich glass inclusions in olivine crystals contain hornblende, which is evidence for a deep source (>25km) for part of the Cl. Gas samples collected in 1986 from 390°–642°C fumaroles on a ramp surrounding the inner summit crater have been oxidized so severely that restoration to an equilibrium composition is not possible. H and O isotope data suggest that these gases are variable mixtures of seawater, FMW, and meteoric steam. These samples are much more H2O-rich (92%–97% H2O) than the dome gases, possibly due to a larger meteoric steam component. The 1986 samples also have higher Cl/S, S/C, and F/Cl ratios, which imply that the magmatic component in these gases is from the more degassed 1976 magma. Thus, the 1987 samples from the lava dome are better indicators than the 1986 samples of degassing within the Augustine magma reservoir, even though they were collected a year later and contain a significant seawater component. Future gas studies at Augustine should emphasize fumaroles on active lava domes. Condensates collected from the same lava-dome fumarole have enrichments ot 107–102 in Cl, Br, F, B, Cd, As, S, Bi, Pb, Sb, Mo, Zn, Cu, K, Li, Na, Si, and Ni. Lower-temperature (200°–650°C) fumaroles around the volcano are generally less enriched in highly volatile elements. However, these lower-termperature fumaroles have higher concentration of rock-forming elements, probably derived from the wall rock.

Lower Bounds for Least Quadratic Non-Residues

Abstract: Let p be a prime, and let n p denote the least positive integer n such that n is a quadratic non-residue mod p. In 1949, Fridlender [F] and Salie [Sa] independently showed that \( {n_p} = \Omega \left( {\log p} \right) \); in other words, there are infinitely many primes p such that \( {n_p} \geqslant c\log p \) for some absolute constant c. In 1971, Montgomery showed that if the Generalized Riemann Hypothesis is true, then $$ {n_p} = \Omega \left( {\log p\log \log p} \right) $$ (1.1)

Balsam Fir on Isle Royale: Effects of Moose Herbivory and Population Density

Abstract: Balsam fir (Abies balsamea) population parameters were analyzed in Isle Royale National Park, Michigan, to assess moose (Alces alces andersoni) herbivory in relation to the population density of both fir and moose. Fir population parameters were determined at nine study sites, each representing a different combination of relative fir and moose density (high, medium, and low levels, respectively). In general, moose suppression of fir height growth and recruitment to the canopy increased with increasing moose density and decreasing fir density. Where fir densities were low, sapling heights were restricted to < 1 m regardless of moose density. In such sites, sapling growth suppression has been continuous since a peak in the moose population in the late 1920s. Canopy fir trees at most sites established prior to arrival of moose on Isle Royale around 1910. At high fir density release from growth inhibition was common following a period of low moose numbers from the mid- 1970s to early 1 980s. Here this release should facilitate recruitment of fir and effect replacement of canopy losses due to senescence. In other areas, however, continuing canopy losses and lack of recruitment due to intensive herbivory by moose will greatly reduce the fir component of the canopy, effectively preventing any return to the fir- dominated forests of the past.

Plastic relaxation of thermoelastic stress in aluminum/ceramic composites

Abstract: The dislocation generation due to a thermoelastic stress in 2024 Al/ceramic (SiC or TiC) composites was studied using transmission electron microscopy Composites containing different ceramic particulates, ceramic volume fraction, and particle size were investigated. Dislocation density profiles were measured as a function of the distance from an Al/ceramic interface and compared with those calculated from an elastoplasticity model which accounts for the volume fraction of the ceramic particles. The intensity of dislocation generation showed a strong particle size dependence: as the ceramic particle size became of the order of a micron, the intensity of dislocation generation increased significantly. With an increase in the volume fraction of the ceramic particles, the dislocation density also increased, and the dislocation structure became a more tangled arrangement. If heat dissipation was taken into account as part of the plastic work, the predicted dislocation densities of the elastoplasticity model were found to be in reasonable agreement with the measured dislocation densities of 109 to 1010 cm−2.

Properties of the interphase in organic matrix composites

Abstract: The mechanical properties of the material surrounding a single carbon fiber in an epoxy matrix have been studied. Properties were determined within 100 nm of the fiber. A pronounced soft interphase was revealed adjacent to the fiber. A single fiber was embedded in a small supported disk of epoxy matrix. The fiber was loaded in tension. Examination of the surface displacements in the resin revealed that the matrix material within 250 nm of the fiber was substantially softer than the matrix far from the fiber. This interphase material was active in creep. Measurement of indentation properties of the matrix around a single fiber showed that the material close to the fiber exhibited an apparent high modulus due to restriction by the fiber. The implications of these findings are discussed.

Growth and maintenance of Thiobacillus ferrooxidans cells

Abstract: A rapid and sensitive spectrophotometric procedure was developed for monitoring the growth of Thiobacillus ferrooxidans in liquid culture. Values determined for the optical densities at 500 nm of washed T. ferrooxidans cell suspensions were directly proportional to both total cell number and total cell protein concentration and provided an accurate measurement of culture growth rate. The utility of this procedure was demonstrated by conducting physiological studies on the influence of CO(2) and FeSO(4) availability on the growth of T. ferrooxidans. In addition, we describe a procedure for the long-term maintenance of cells T. ferrooxidans that ensures culture purity and genetic stability.

Worldwide dispersal of ash and gases from earth's largest known eruption: Toba, Sumatra, 75 ka

Abstract: The eruption of the Youngest Toba Tuff (YTT) occurred 75 ± 2 ka in North Sumatra (2°45′N, 98°45′E). The eruption produced at least 2800 km3 of dense rock equivalent (DRE) rhyolite magma (7 × 1018 g). Much of the volume of magma was preserved as a non-welded outflow sheet covering 20,000–30,000 km2 and a thick, welded intracaldera tuff. At least 800 km3 (2 × 1018 g) of Toba ash was deposited in an extensive ash blanket over the Indian Ocean and Southern Asia. Detailed studies of the chemistry of minerals and glasses in pumices from the YTT enable estimation of the minimum masses of gaseous components released to earth's atmosphere during the eruption: H2O:. The high eruption rate, with the entire event lasting perhaps 9–14 days make stratospheric venting of a significant fraction of these gases and associated silicate ash and aerosol particles likely. The masses of ash and gases released is nearly two orders of magnitude higher than any known historic eruption.

The role of pathos in the decision‐making process: A study in the rhetoric of science policy

Abstract: Over the course of this century, science and technology policy issues such as the management of hazardous wastes and the protection of endangered species have become increasingly common and important. To respond constructively to such issues, either by petitioning policy makers or by shaping policy themselves, nonscientists must be prepared to interpret, criticize, and synthesize complex scientific and ethical arguments. The experience of the Cambridge Experimentation Review Board suggests that in spite of some cultural bias against pathos, emotional appeals play a vital role in the shaping of science policy decisions. This paper argues that the character of the audience is a key factor in determining whether a given emotional appeal will be considered appropriate; it further argues that a renewed emphasis on rhetorical studies will help to prepare the public for a constructive role in the shaping of science policy.

Load-independent class E power inverters. I. Theoretical development

Abstract: An analysis is presented for a class-E power inverter that exhibits any of the following characteristics: (1) load-independent, nonzero output voltage, but not load-independent efficiency; (2) load-independent nonzero efficiency, but not load output voltage; (3) simultaneous load-independent, nonzero output voltage and load-independent nonzero efficiency. Solutions for a class-E inverter with load-independent, nonzero output voltage and 100% efficiency are given. The infinite set of solutions is reduced by practical considerations. Circuit parameters for practical load-independent class-E inverters are provided. >

Wet process for fly ash beneficiation

Abstract: A wet process for the beneficiation of a fly ash by-product has the following steps: a) forming a slurry mixture of a fly ash material and a liquid; b) gravitationally separating and collecting a first material fraction of the fly ash having a density less than the liquid by skimming off floating slurry material; c) separating a first magnetic fraction from the slurry by subjecting the slurry to a magnetic field of from about 300 gauss to about 10 kilogauss; d) separating the unburned carbon from the remaining slurry components by adding an effective amount of an oil having a carbon chain greater than octane, and a frothing agent whereby the oil coats the unburned carbon forming hydrophobic carbon materials and inducing air into the system for frothing the slurry mixture wherein the hydrophobic unburned carbon froths to the surface and is removed by skimming off the frothing layer; and e) collecting the remaining fraction of silicate spheres and silicates.

Crashworthy Behaviour of Thin-Walled Tubes of Fibreglass Composite Materials Subjected to Axial Loading

Abstract: In this paper we report on small scale modelling of fracture mechanisms and large scale deformation of fibre-reinforced composite materials when circular thin-walled tubes are subjected to axial collapse. Contrary to the mechanism of energy absorption in the case of ductile materials, energy absorption for brittle composite materials is achieved by material fragmentation, i.e., the mechanism of fracture dominates the phenomenon rather than the plastic deformation. The effect of composite material properties and the tube geometry on the crashworthy characteristics of the tubular structural components is investigated with the aim in mind of the cost-effective design of structural elements in vehicles.

An exact analysis of class E amplifiers with finite DC-feed inductance at any output Q

Abstract: Previous analyses of class E amplifiers have required infinite output network Q and/or infinite DC-feed inductance. A Laplace-transform technique is applied to class E circuits with neither of these restrictions. The analysis presented is shown to have excellent agreement with observed circuit performance. >

Past atmospheric deposition of metals in northern Indiana measured in a peat core from Cowles Bog

Abstract: A peat core from a calcareous fen was used to assess past metal accumulation from atmospheric sources in northern Indiana. Total concentrations of Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, and Zn were measured at intervals along the core, which were dated by {sup 210}Pb, radiocarbon, and pollen analysis. The deposition of airborne metal particulates rose dramatically from presettlement levels as industrialization occurred upwind, with accumulation rates for some metals increasing by 2 orders of magnitude. Recent accumulation rates are about half of the peak rates of the 1970s, presumably because of emission controls and reduced production. This study, the first such record from a calcareous fen, should be less affected by postdepositional mobility than records from acidic peatlands. This method of retrospective, long-term monitoring of airborne particulates can be applied in many areas lacking such records.

On the microscopic origin of the plastic spin

Abstract: Considering the configuration of a single slip and employing a scale invariance argument, it is possible to deduce a set of “microscopic” plastic flow relations having a direct counterpart in the “macroscopic” formulation of plasticity and viscoplasticity. In particular, a microscopic form of the plastic spin and its macroscopic counterpart for the case of anisotropy induced by kinematic hardening are obtained in terms of elementary physical arguments. Moreover the evolution equation for the back-stress is rigorously derived. Parameters which were assumed to be constant and/or independent from each other in a macroscopic development, are now found to be interrelated and dependent on the accumulated plastic strain. These findings are used for the analysis of the simple shear problem, especially in evaluating the development of the axial stress normal to the shear plane. A preliminary qualitative comparison with available data from fixed-end torsion experiments is discussed.

Moose teeth as monitors of environmental isotopic parameters

Abstract: The radiocarbon activities of amino acids isolated from crown first molar dentin of moose born between 1948 and 1984 on Isle Royale National Park, USA closely follows the bomb radiocarbon signal generated from atmospheric nuclear weapons testing. This demonstrates that these amino acids are metabolically inert and have recorded the isotopic parameters of the environment during the first year or two of the animal's life. The moose teeth amino acids provide both carbon and nitrogen isotopic chronologies for Isle Royale for a period of nearly four decades. The carbon isotopic record reflects both anthropogenic alterations of the global atmospheric carbon cycle (the “Suess” effect), and changes in forest ecology and moose feeding habitat. The nitrogen isotopic chronology is more variable than the carbon record and is the result of environmental and biological factors which are poorly understood.

The injection of sulfuric acid aerosols in the stratosphere by the El Chichón volcano and its related hazards to the international air traffic

Abstract: With respect to atmospheric impact, the 1982 eruption of the El Chichon volcano in Mexico is one of the most significant volcanic events of this century. The presence in the stratosphere, during several years, of an unusally high amount of sulfuric acid aerosols produced by this eruption is thought to be responsible for severe windshield damages on high-flying commercial jets. This problem took epidemic proportions in 1983–1984 and the cost to commercial aviation companies is estimated at several tens of millions of U.S. dollars.

Toward quantifying infrared clutter

Abstract: Target detection in clutter depends sensitively on the spatial structure of the latter. In particular, it is the ratio of the target size to the clutter inhomogeneity scale which is of crucial importance. Indeed, looking for the leopard in the background of leopard skin is a difficult task. Hence quantifying thermal clutter is essential to the development of successful detection algorithms and signature analysis. This paper describes an attempt at clutter characterization along with several applications using calibrated thermal imagery collected by the Keweenaw Research Center. The key idea is to combine spatial and intensity statistics of the clutter into one number in order to characterize intensity variations over the length scale imposed by the target. Furthermore, when properly normalized, this parameter appears independent of temporal meteorological variation, thereby constituting a background scene invariant. This measure has a basis in analysis of variance and is related to digital signal processing fundamentals. Statistical analysis of thermal images is presented with promising results.

Isothermal Reaction Kinetics of Kraft Delignification of Douglas-Fir

Abstract: Kraft delignification of Douglas-fir (Pseudotsuga menziesii) wood meal was carried out under an instantaneous isothermal condition with a liquor-to-wood ratio of 50 to investigate the effects of reaction temperature and chemical concentration on the rate of delignification. The temperatures studied were in the range of 120 to 175°C. Three levels of [HO−l] and three levels of [HS−l] concentrations were investigated. In each case an efficient mechanical agitation of the pulping liquor was maintained and the delignification was extended to reach its completion. Using a nonlinear regression analysis on the delignification results, a single kinetics equation was resolved to describe the effect of temperature and chemical concentration on the rates of delignification for the initial, bulk, and final phases. This equation also revealed that the amounts of lignin removed due to the chemical reactions in the initial, bulk, and final phases were 18.8, 71.4, and 3.8%, respectively. About 6% of the total lig...