Showing papers by "Michigan Technological University published in 1995"

Creative problem solving

Abstract: Problem solving, as commonly taught in schools, is an analytical or procedural approach. This approach almost exclusively employs left-brain thinking modes, is competitive, and relies on individual effort. However, creative problem solving is a framework that encourages whole-brain, iterative thinking in the most effective sequence; it is cooperative in nature and is most productive when done as a team effort.

Atmospheric CO2, soil nitrogen and turnover of fine roots

Abstract: summary In most natural ecosystems a significant portion of carbon fixed through photosynthesis is allocated to the production and maintenance of fine roots, the ephemeral portion of the root system that absorbs growth-limiting moisture and nutrients. In turn, senescence of fine roots can be the greatest source of C input to forest soils. Consequently, important questions in ecology entail the extent to which increasing atmospheric CO2 may alter the allocation of carbon to, and demography of, fine roots. Using microvideo and image analysis technology, we demonstrate that elevated atmospheric CO2 increases the rates of both fine root production and mortality. Rates of root mortality also increased substantially as soil nitrogen availability increased, regardless of CO2 concentration. Nitrogen greatly influenced the proportional allocation of carbon to leaves vs. fine roots. The amount of available nitrogen in the soil appears to be the most important factor regulating fine root demography in Populus trees.

Dietary Protein and Energy as Determinants of Food Quality: Trophic Strategies Compared

Abstract: The effects of dietary protein and energy on ingestion and growth were determined for nutrient ranges that correspond to primary foods in freshwaters: algae, aquatic macrophytes and organic detritus. Sixteen diets containing four levels of metabo- lizable energy (ME) (3.1, 6.7, 10.5, 14.1 kJ/g) and four levels of protein (3.0, 13.2, 23.2, 33.4 mg/kJ ME) were each fed ad libitum to four replicate groups of juvenile Tilapia aurea for 42 d. Protein, energy, and protein-energy interaction affected both ingestion and growth (two-way ANOVA, all P < 0.01). Increased ingestion largely compensated for lower energy levels within each protein level. Growth was proportional to diet protein content, and ingestion did not compensate for protein limitation. A second-order polynomial for growth as a function of diet protein content and energy assimilation rate fitted by linear regression accounts for 91% of variation in growth, and provides a model for comparison of the relative importance of protein and energy as nutritional constraints for animals feeding on invertebrate prey, algae, aquatic macrophytes, and organic detritus. Protein appears to be the primary constraint to food value of macrophytes, and detritus, and we predict from our results that consumers of these materials will increase growth most by feeding selectively on the most protein-rich material available, as has been observed. In contrast, growth of animals feeding on algae will be increased most by increased ingestion. Omnivory is interpreted as a compromise strategy in which protein from scarce animal prey is comple- mented by energy from abundant primary foods.

Temperature Effects on Kinetics of Microbial Respiration and Net Nitrogen and Sulfur Mineralization

Abstract: Global climate change may impact the cycling of C, N, and S in forest ecosystems because increased soil temperatures could alter rates of microbially mediated processes. We studied the effects of temperature on microbial respiration and net N and S mineralization in surface soils from four northern hardwood forests in the Great Lakes region. Soil samples were incubated in the laboratory at five temperatures (5, 10, 15, 20, and 25°C) for 32 wk. Headspace gas was analyzed for CO2-C at 2-wk intervals, and soils were extracted to determine inorganic N and S. Cumulative respired C and mineralized N and S increased with temperature at all sites and were strongly related (r2 = 0.67 to 0.90, significant at P = 0.001) to an interaction between temperature and soil organic C. Production of respired C and mineralized N was closely fit by first-order kinetic models (r2 > 0.94, P = 0.001), whereas mineralized S was best described by zero-order kinetics. Contrary to common assumptions, rate constants estimated from the first-order models were not consistently related to temperature, but apparent pool sizes of C and N were highly temperature dependent. Temperature effects on microbial respiration could not be accurately predicted using temperature-adjusted rate constants combined with a constant pool size of labile C. Results suggest that rates of microbial respiration and the mineralization of N and S may be related to a temperature-dependent constraint on microbial access to substrate pools. Simulation models should rely on a thorough understanding of the biological basis underlying microbially mediated C, N, and S transformations in soil.

Thinking Preferences of Engineering Students: Implications for Curriculum Restructuring

Abstract: The thinking preferences of engineering students at the University of Toledo have been assessed in a longitudinal study, using the Herrmann Brain Dominance Instrument (HBDI). The scores and profiles reveal thinking preferences in four different ways of thinking and “knowing”: A = analytical-logical-quantitative, B = sequential-organized-detailed, C = interpersonal-sensory-kinesthetic, and D = innovative-holistic-conceptual thinking. With the HBDI, we have a tool that can assess the effects of curriculum restructuring. Data from 1990–1993 fall freshmen classes and 1991–1994 spring senior classes have been evaluated, where the 1994 seniors are the first group for which freshmen data are available. Conclusions drawn from the results are: 1) Overall, there has been a shift from “plug-and-chug” quadrant B thinking to increased “creative” quadrant D thinking, because more students with strong quadrant D preferences are being developed and retained, primarily due to the new creative problem solving course. 2) Avoidance of quadrant C thinking (teamwork skills) is persisting and creates classroom climates that are uncomfortable for some students, a high percentage being females. Students are not developing the teamwork and interpersonal thinking skills demanded by industry. 3) A majority of students are still being cloned in the A-dominant profile of the faculty. Students who have developed independent ways of practicing right-brain thinking and all students who were involved in creative problem solving as class assistants became more whole-brained or right-brained. Quadrant C and D thinking activities must be integrated into the curriculum each term for students to develop their full potential and reinforce the whole-brain thinking skills introduced in the first-year creative problem solving course.

Ice in the 1994 Rabaul eruption cloud : implications for volcano hazard and atmospheric effects

Abstract: VOLCANIC clouds are an important natural hazard to aircraft1, and host chemical reactions that interest both volcanologists2,3 and atmospheric scientists4-6. Ice has been suggested as a possible component of eruption clouds7, but there has been no direct evidence for its presence. Here we report the detection, using a satellite-borne infrared sensor, of ≳ 2 million tonnes of ice in the cloud produced by the September 1994 eruption of Rabaul volcano, in Papua New Guinea. The cloud also contained relatively low levels of sulphur dioxide (80 ± 50 kilotonnes), compared with other stratospheric eruption clouds. The unusual aspects of this cloud may be related to the entry of sea water into the volcanic vent, and its participation in the eruption column. Past eruptions that occurred in similar (coastal) settings, such as those of Krakatau and Santorini, might have had less effect on the atmosphere than their volume alone would suggest, because the presence of ice may decrease the residence time of ash and sulphur in the atmosphere. In addition, the ability of ice to mask the characteristic spectral signature of volcanic ash will increase the difficulty of designing airborne ash detection systems for aviation safety.

Carbon allocation and partitioning in aspen clones varying in sensitivity to tropospheric ozone.

Abstract: Clones of aspen (Populus tremuloides Michx.) were identified that differ in biomass production in response to O(3) exposure. (14)Carbon tracer studies were used to determine if the differences in biomass response were linked to shifts in carbon allocation and carbon partitioning patterns. Rooted cuttings from three aspen Clones (216, O(3) tolerant; 271, intermediate; and 259, O(3) sensitive) were exposed to either charcoal-filtered air (CF) or an episodic, two-times-ambient O(3) profile (2x) in open-top chambers. Either recently mature or mature leaves were exposed to a 30-min (14)C pulse and returned to the treatment chambers for a 48-h chase period before harvest. Allocation of (14)C to different plant parts, partitioning of (14)C into various chemical fractions, and the concentration of various chemical fractions in plant tissue were determined. The percent of (14)C retained in recently mature source leaves was not affected by O(3) treatment, but that retained in mature source leaves was greater in O(3)-treated plants than in CF-treated plants. Carbon allocation from source leaves was affected by leaf position, season, clone and O(3) exposure. Recently mature source leaves of CF-treated plants translocated about equal percentages of (14)C acropetally to growing shoots and basipetally to stem and roots early in the season. When shoot growth ceased (August 16), most (14)C from all source leaves was translocated basipetally to stem and roots. At no time did mature source leaves allocate more than 6% of (14)C translocated within the plant to the shoot above. Ozone effects were most apparent late in the season. Ozone decreased the percent (14)C translocated from mature source leaves to roots and increased the percent (14)C translocated to the lower stem. In contrast, allocation from recently mature leaves to roots increased. Partitioning of (14)C among chemical fractions was affected by O(3) more in source leaves than in sink tissue. In source leaves, more (14)C was incorporated into the sugar, organic acid and lipids + pigments fractions, and less (14)C was incorporated into starch and protein fractions in O(3)-treated plants than in CF-treated plants. In addition, there were O(3) treatment interactions between leaf position and clones for (14)C incorporation into different chemical fractions. When photosynthetic data were used to convert percent (14)C transported to the total amount of carbon transported on a mass basis, it was found that carbon transport was controlled more by photosynthesis in the source leaves than proportional changes in allocation to the sinks. Ozone decreased the total amount of carbon translocated to all sink tissue in the O(3)-sensitive Clone 259 because of decreases in photosynthesis in both recently mature and mature source leaves. In contrast, O(3) had no effect on carbon transport from recently mature leaves to lower shoots of either Clone 216 or 271, had no significant effect on transport to roots of Clone 216, and increased transport to roots of Clone 271. The O(3)-induced increase in transport to roots of Clone 271 was the result of a compensatory increase in upper leaf photosynthesis and a relatively greater shift in the percent of carbon allocated to roots. In contrast to those of Clone 271, recently mature leaves of Clone 216 maintained similar photosynthetic rates and allocation patterns in both the CF and O(3) treatments. We conclude that Clone 271 was more tolerant to O(3) exposure than Clone 216 or 259. Tolerance to chronic O(3) exposure was directly related to maintenance of high photosynthetic rates in recently mature leaves and retention of lower leaves.

Interacting effects of soil fertility and atmospheric CO2 on leaf area growth and carbon gain physiology in Populus × euramericana (Dode) Guinier

Abstract: SUMMARY Two important processes which may limit productivity gains in forest ecosystems with rising atmospheric CO2are reduction in photosynthetic capacity following prolonged exposure to high CO2 and diminution of positive growth responses when soil nutrients, particularly N, are limiting. To examine the interacting effects of soil fertility and CO2 enrichment on photosynthesis and growth in trees we grew hybrid poplar (Populus × euramericana) for 158 d in the field at ambient and twice ambient CO2 and in soil with low or high N availability. We measured the timing and rate of canopy development, the seasonal dynamics of leaf level photosynthetic capacity, respiration, and N and carbohydrate concentration, and final above- and belowground dry weight. Single leaf net CO2 assimilation (A) increased at elevated CO2 over the majority of the growing season in both fertility treatments. At high fertility, the maximum size of individual leaves, total leaf number, and seasonal leaf area duration (LAD) also increased at elevated CO2, leading to a 49% increase in total dry weight. In contrast, at low fertility leaf area growth was unaffected by CO2 treatment. Total dry weight nonetheless increased 25% due to CO2 effects on A. Photosynthetic capacity (A at constant internal p(CO2), ((C1)) was reduced in high CO2 plants after 100 d growth at low fertility and 135 d growth at high fertility. Analysis of A responses to changing C1 indicated that this negative adjustment of photosynthesis was due to a reduction in the maximum rate of CO2 fixation by Rubisco. Maximum rate of electron transport and phosphate regeneration capacity were either unaffected or declined at elevated CO2. Carbon dioxide effects on leaf respiration were most pronounced at high fertility, with increased respiration mid-season and no change (area basis) or reduced (mass basis) respiration late-season in elevated compared to ambient CO2 plants. This temporal variation correlated with changes in leaf N concentration and leaf mass per area. Our results demonstrate the importance of considering both structural and physiological pathways of net C gain in predicting tree responses to rising CO2 under conditions of suboptimal soil fertility.

Imaging through turbulence

Abstract: Introduction Overview of the Problem Area Historical Overview of Imaging Through Turbulence Overview of the Book Background: Fourier and Statistical Optics Fourier Optics Statistical Optics Turbulence Effects on Imaging Systems Index of Refraction Fluctuations in the Atmosphere Statistics of Index of Refraction Fluctuations Wave Propagation through Random Media First-Order Turbulence Effects on Incoherent Imaging Modal Expansions of Phase Perturbation Phase Screen Generation Speckle Imaging Techniques Introduction Overview of Speckle Imaging Speckle Interferometry Fourier Phase Estimation Techniques Image Reconstruction for Speckle Imaging Conclusion Adaptive Optical Imaging Systems Introduction Factors that Degrade AOI Systems Performance Adaptive Optical System Components and Models AOI System Performance Modeling Summary Hybrid Imaging Techniques Introduction Deconvolution from Wavefront Sensing Methods Involving Adaptive Optics Conclusion Index

Cramer-Rao lower bounds for a damped sinusoidal process

Abstract: The Cramer-Rao lower bounds (CRLBs) for the parameter estimators of a damped sinusoidal process are derived in this paper. Succinct matrix expressions for CRLB's of frequency, damping factor, amplitude, and initial phase are given for both scalar and vector processes. The relationships between the CRLBs of the characteristic parameters are established in the general multimode case. In particular, explicit, closed-form expressions for the single mode scalar/vector-damped/undamped cases are provided. >

Photosynthetic productivity of aspen clones varying in sensitivity to tropospheric ozone.

Abstract: Rooted cuttings from three aspen (Populus tremuloides Michx.) clones (216, 271 and 259, classified as high, intermediate and low in O(3) tolerance, respectively) were exposed to either diurnal O(3) profiles simulating those of Michigan's Lower Peninsula (episodic treatments), or diurnal square-wave O(3) treatments in open-top chambers in northern Michigan, USA. Ozone was dispensed in chambers ventilated with charcoal-filtered (CF) air. In addition, seedlings were compared to rooted cuttings in their response to episodic O(3) treatments. Early in the season, O(3) caused decreased photosynthetic rates in mature leaves of all clones, whereas only the photosynthetic rates of recently mature leaves of the O(3)-sensitive Clone 259 decreased in response to O(3) exposure. During midseason, O(3) caused decreased photosynthetic rates of both recently mature and mature leaves of the O(3)-sensitive Clone 259, but it had no effect on the photosynthetic rate of recently mature leaves of the O(3)-tolerant Clone 216. Late in the season, however, photosynthetic rates of both recently mature and mature leaves of Clone 216 were lower than those of the control plants maintained in CF air. Ozone decreased the photosynthetic rate of mature leaves of Clone 271, but it increased or had no effect on the photosynthetic rate of recently mature leaves. Photosynthetic response patterns of seedlings to O(3) treatment were similar to those of the clones, but total magnitude of the response was less, perhaps reflecting the diverse genotypes of the seedling population. Early leaf abscission was observed in all clones exposed to O(3); however, Clones 216 and 259 lost more leaf area than Clone 271. By late August, leaf area in the highest O(3) treatment had decreased relative to the controls by 26, 24 and 9% for Clones 216, 259 and 271, respectively. Ozone decreased whole-tree photosynthesis in all clones, and the decrease was consistently less in Clone 271 (23%) than in Clones 216 (56%) and 259 (56%), and was accompanied by declines in total biomass of 19, 28 and 47%, respectively. The relationship between biomass and whole-tree photosynthesis indicates that the negative impact of O(3) on biomass in the clones was determined largely by lower photosynthetic productivity of the foliage, rather than by potential changes in the carbon relations of other plant organs.

Modification of Al-Si alloys: Microstructure, thermal analysis, and mechanisms

Abstract: In aluminum-silicon cast alloys, the shapes of the silicon phase and the general solidification pattern can be changed by the cooling conditions and by minor additions to the melt. The minor additions either cause modification (sodium, strontium, and other metals) or refine the primary silicon in hypereutectic alloys (phosphorus and elements of Group V-B). Detailed examination of the modified microstructures and analysis of cooling curves are compatible with a modification mechanism involving growth rather than nucleation kinetics.

Biosynthesis and distribution of insect-molting hormones in plants--a review.

Abstract: Insect-molting hormones, phytoecdysteroids, have been reported to occur in over 100 plant families. Plants, unlike insects, are capable of the biosynthesis of ecdysteroids from mevalonic acid, and in several cases the biosynthesis of phytoecdysteroids was also demonstrated to proceedvia sterols.Spinacia oleracea (spinach) biosynthesizes polypodine B and 20-hydroxyecdysone, which is the predominant insect-molting hormone found in plant species. The onset of ecdysteroid production in spinach requires the appropriate ontogenetic development within the plant, which is related to leaf development. In spinach, lathosterol is the biosynthetic precursor to ecdysone and 20-hydroxyecdysone. Phosphorylated ecdysteroid intermediates, particularly ecdysone-3-phosphate, are required during biosynthesis. Polyphosphorylated forms of ecdysteroids are putative regulatory components of the pathway. During spinach development, the 20-hydroxyecdysone is transported from the sites of biosynthesis to the apical regions. An analysis of the physiological data available suggests that different species may synthesize ecdysteroids in various organs and distribute these ecdysteroids to other sites. Annual plants appear to concentrate ecdysteroids in the apical regions, including flowers and seeds. Perennial plants may recycle their ecdysteroids between their deciduous and their perennial organs over the growing season. Further investigations of ecdysteroid biosynthesis and physiology within plants will be required before an acceptable system can be designed to test phytoecdysteroid effectivenessin vivo against insect herbivory.

The nucleation and growth of graphite—the modification of cast iron

Abstract: It is considered that all forms of graphite, precipitating from a metallic solution, must evolve from a basic hexagonal ring structure, growing into an open monolayer sheet. Subsequent growth of this precursor can lead to multi-layer sheets—flake graphite, to rolled or wrapped concentric shells—spheroidal graphite, or, possibly, to saturated fullerene units. The molecular attachment kinetics which might favor these alternatives are briefly discussed and compared with experimental evidence. Spheroidal graphite is the preferred morphology in a clean melt, flake graphite is an impurity modified form and growth to form fullerenes is presently unpredictable, but is considered to be improbable.

Process modeling of mechanical alloying: overview

Abstract: Recent efforts at modeling the mechanics and dynamics of mechanical alloying are summarized. The modeling is described from two perspectives. One considers the deformation response and the fracture and welding tendencies of powder particles entrapped between colliding grinding media in an individual collision. We call this local modeling. Fundamental and phenomenological approaches to local modeling have been undertaken, and these are described here as are numerical applications of the approaches. We have termed the second type of modeling global modeling. Global modeling concerns itself with device specific characteristics, and has potential for improving MA devices. Global modeling also serves to provide parameters that are necessary to best utilize local modeling.

Belowground responses to rising atmospheric CO2: Implications for plants, soil biota and ecosystem processes

Abstract: As atmospheric CO2 concentrations increase there almost certainly will be alterations in the flux of C from plants to the soil. It is likely that such alterations will be accompanied by changes in the allocation of C to organic structures and to soil processes. These changes have the potential for further altering the structure and function of terrestrial ecosystems. While there has been increasing recognition of the importance of soil-mediated responses to global climate change, the nature and magnitude of these responses are not well understood.

The influence of cytokinins in nitrate regulation of nitrate reductase activity and expression in barley

Abstract: The responses of nitrate reductase (NR) activity and levels of NR-mRNA to environmental nitrate and exogenous cytokinins are characterised in roots and shoots of barley (Hordeum vulgare L., cv. Golf), using a chemostate-like culture system for controlling nitrate nutrition. Experiments were mainly performed with split root cultures where nitrate-N was supplied at a constant relative addition rate of 0.09 day −1 , and distributed between the subroots in a ratio of 20%:80%. The subroot NR-mRNA level and NR activity, as well as the endogenous level of zeatin riboside (ZR), increased when the local nitrate supply to one of the subroots was increased 4-fold by reversing the nitrate addition ratio (i.e. from 20%:80% to 80%:20%). Also shoot levels of ZR, NR-mRNA and NR activity increased in response to this treatment, even though the total nitrate supply remained unaltered. External supply of ZR at 0.1 μM caused an approximately 3-fold increase in root ZR levels within 6 h, which is comparable to the nitrate-induced increase in root ZR. External application of ZR, zeatin, isopentenyl adenine or isopentenyl adenosine at 0.1 μM caused from insignificant to 25% increases in NR-mRNA and activity in roots and up to 100% stimulation in shoots, whereas adenine or adenosine had no effect. No synergistic effects of perturbed nitrate supply and cytokinin application were detected in either roots or shoots. The translocation of nitrate from the root to the shoot was unaffected by application of ZR or switching the nitrate distribution ratio between subroots. The data give arguments for a physiological role of cytokinins in the response of root and shoot NR to environmental nitrate availability. The nature and limitations of the physiological role of cytokinins are discussed

Dynamics of OH (X2 Pi , v=0) in high-energy atmospheric pressure electrical pulsed discharge

Abstract: Time transients of the number density of the hydroxyl radical ground state X2 Pi (v=0) formed in the DC high-energy atmospheric pressure pulsed discharge were measured by means of laser-induced fluorescence. The frequency doubled dye laser was tuned to the A2 Sigma from X2 Pi (v'=1 from v"=0) transition at 282 nm while emission at 309 nm from A2 Sigma to X2 Pi (v'=0 to v"=0) band, was observed. The discharge peak current Imax varied from 10-2 to 10 A, and the time duration was from 500 ns to 50 mu s. The discharge was operated at repetition rate of 10 Hz. The population of v"=0 of OH reaches the steady state within the first 20 mu s of the discharge and its value is independent on the current for Imax>or=0.2 A. The significant build-up of v"=0 state population was observed after the discharge pulse. The hydroxyl ground state number density reaches its maximum value approximately 100 mu s after the discharge and is up to three times larger than during the discharge pulse. This increase of v"=0 population is attributed to the vibrational relaxation within X2 Pi state.

Repetitive stratal patterns in a foreland basin sandstone and their possible tectonic significance

Abstract: Two distinctive, repetitive stratal patterns within members of the Upper Cretaceous Blackhawk Formation in Utah are recognized by comparison of (1) progradational distances of individual parasequences within each member and (2) the position of the updip termination of marine facies for each parasequence. The oldest parasequence within each member always progrades substantially farther than the younger parasequences within the same member, regardless of whether these parasequences are separated by sequence boundaries. The pattern of progradational distances results in an initial progradational to later aggradational stacking pattern within each member. This pattern is observed in all members of the Blackhawk Formation where there is sufficient outcrop exposure to trace the nonmarine-to-marine transition, which is used to establish the progradational distances. These stratal patterns are interpreted to define the path of relative change of sea level through time within the Cretaceous foreland basin and may provide information characterizing thrust-sheet emplacement. Flooding events bounding parasequences may represent periods of punctuated thrusting, with the main flooding surface (member boundaries) representing the period of greatest thrust-sheet movement.

Glasslike behavior in a nanostructured Fe/Cu alloy

Abstract: In this article, the authors report the observation of shear bands and perfectly plastic behavior, typical of metallic glasses, in an Fe-Cu alloy with grain sizes in the 100 nm range. A strengthening effect with decreasing grain size was also observed, and the shear bands occurred on planes oriented at about 40 deg from the tensile axis instead of the maximum shear plane of 45 deg, as has been observed in amorphous polymers.

Dissolved organic carbon in northern hardwood stands with differing acidic inputs and temperature regimes

Abstract: We monitored concentrations and fluxes of dissolved organic carbon (DOC) in throughfall and forest floor solutions in two northern hardwood stands located at the northern and southern end of a latitudinal acidic deposition and air temperature gradient in the Great Lakes Region to determine if DOC levels are altered by regional and temporal variation in acidic inputs and temperature. Amounts of precipitation received at the two sites were similar, but precipitation pH and air temperature, respectively, averaged 4.83 and 13.9°C at the northern gradient site and 4.29 and 15.1°C at the southern gradient site. Volume weighted DOC concentrations in throughfall were significantly greater at the northern (20.5 mg L -1 ) than the southern (15.9 mg L -1 ) site, but these differences in DOC levels were caused by the differing amounts of throughfall passing through the canopy of the two sites rather than levels of precipitation acidity or air temperature. Temporal variation in the levels of DOC in throughfall was not related to the variation in either precipitation acidity or air temperature. Like throughfall, levels of DOC in forest floor solutions were not found to be altered by acidic inputs. However, DOC in these solutions increased with seasonal increases in soil temperature. A regression equation relating seasonal variation in soil temperature and forest floor concentrations of DOC estimated that an observed 2.1°C difference in soil temperature at the two sites during the growing season could represent as much as 3.7 mg L -1 difference in forest floor solution concentrations of DOC.