Showing papers by "University of Maine published in 1997"

Iron and grazing constraints on primary production in the central equatorial Pacific: An EqPac synthesis

Abstract: Recent studies in the central equatorial Pacific allow a comprehensive assessment of phytoplankton regulation in a high-nutrient, low-chlorophyll (HNLC) ecosystem. Elemental iron enters the euphotic zone principally via upwelling and is present at concentrations (530 PM) well below the estimated half-saturation constant (120 PM) for the large cells that bloom with iron enrichment. In addition, the meridional trend in quantum yield of photosynthesis suggests that even the dominant small phytoplankton are held below their physiological potential by iron deficiency. Grazing by microzooplankton dominates phytoplankton losses, accounting for virtually all of the measured phytoplankton production during El Nina conditions and -66% during normal upwelling conditions, with mesozooplankton grazing and lateral advection closing the balance. Nitrate uptake is strongly correlated with the pigment biomass of diatoms, which increase in relative abundance during normal upwelling conditions. Nonetheless, the f-ratio remains low (0.07-0.12) under all conditions. Iron budgets are consistent with the notions that new production is determined by the rate of new iron input to the system while total production depends on efficient iron recycling by grazers. Although the limiting substrates differ, the interactions of resource limitation and grazing in HNLC regions are conceptually similar to the generally accepted view for oligotrophic subtropical regions. In both systems, small dominant phytoplankton grow at rapid, but usually less than physiologically maximal, rates; they are cropped to low stable abundances by microzooplankton; and their sustained high rates of growth depend on the remineralized by-products of grazing.

Quantitative analysis of Drosophila period gene transcription in living animals.

Abstract: To determine the in vivo regulatory pattern of the clock gene period (per), the authors recently developed transgenic Drosophila carrying a luciferase cDNA fused to the promoter region of per. They have now carried out noninvasive, high time-resolution experiments allowing high-throughput monitoring of circadian bioluminescence rhythms in individual living adults for several days. This immediately solved several problems (resulting directly from individual asynchrony within a population) that have accompanied previous biochemical experiments in which groups of animals were sacrificed at each time point. Furthermore, the authors have developed numerical analysis methods for automatically determining rhythmicity associated with bioluminescence records from single flies. This has revealed some features of per gene transcription that were previously unappreciated and provides a general strategy for the analysis of rhythmic time series in the study of molecular rhythms.

Persistent nuclear ribosomal DNA sequence polymorphism in the Amelanchier agamic complex (Rosaceae).

Abstract: Individual plants of several Amelanchier taxa contain many polymorphic nucleotide sites in the internal transcribed spacers (ITS) of nuclear ribosomal DNA (nrDNA). This polymorphism is unusual because it is not recent in origin and thus has resisted homogenization by concerted evolution. Amelanchier ITS sequence polymorphism is hypothesized to be the result of gene flow between two major North American clades resolved by phylogenetic analysis of ITS sequences. Western North American species plus A. humilis and A. sanguinea of eastern North America form one clade (A), and the remaining eastern North American Amelanchier make up clade B. Five eastern North American taxa are polymorphic at many of the nucleotide sites where clades A and B have diverged and are thought to be of hybrid origin, with A. humilis or A. sanguinea as one parent and various members of clade B as the other parent. Morphological evidence suggests that A. humilis is one of the parents of one of the polymorphic taxa, a microspecies that we refer to informally as A. "erecta." Sequences of 21 cloned copies of the ITS1-5.8S gene-ITS2 region from one A. "erecta" individual are identical to A. humilis sequence or to the clade B consensus sequence, or they are apparent recombinants of A. humilis and clade B ITS repeats. Amelanchier "erecta" and another polymorphic taxon are suspected to be relatively old because both grow several hundred kilometers beyond the range of one of their parents. ITS sequence polymorphisms have apparently persisted in these two taxa perhaps because of polyploidy and/or agamospermy (asexual seed production), which are prevalent in the genus.

The fungal mitochondrial genome project: evolution of fungal mitochondrial genomes and their gene expression.

Abstract: The goal of the fungal mitochondrial genome project (FMGP) is to sequence complete mitochondrial genomes for a representative sample of the major fungal lineages; to analyze the genome structure, gene content, and conserved sequence elements of these sequences; and to study the evolution of gene expression in fungal mitochondria. By using our new sequence data for evolutionary studies, we were able to construct phylogenetic trees that provide further solid evidence that animals and fungi share a common ancestor to the exclusion of chlorophytes and protists. With a database comprising multiple mitochondrial gene sequences, the level of support for our mitochondrial phylogenies is unprecedented, in comparison to trees inferred with nuclear ribosomal RNA sequences. We also found several new molecular features in the mitochondrial genomes of lower fungi, including: (1) tRNA editing, which is the same type as that found in the mitochondria of the amoeboid protozoan Acanthamoeba castellanii; (2) two novel types of putative mobile DNA elements, one encoding a site-specific endonuclease that confers mobility on the element, and the other constituting a class of highly compact, structured elements; and (3) a large number of introns, which provide insights into intron origins and evolution. Here, we present an overview of these results, and discuss examples of the diversity of structures found in the fungal mitochondrial genome.

Teacher Efficacy, Supervision, and the Special Education Resource-Room Teacher

Abstract: The Gibson and Dembo Teacher Efficacy Scale was modified for use in the special education resource-room context. A factor analysis of the modified instrument resulted in a factor structure comparable to one based on regular-education teachers, as reported in prior research. The relation between instructional supervision and teacher efficacy among these teachers was also examined. With sex, age, resource-room tenure, and job satisfaction held constant, the perceived utility—but not frequency—of supervision was significantly related to teacher efficacy. The implications of these findings for both research and practice in the special education context are considered.

Relations among children's social goals, implicit personality theories, and responses to social failure

Abstract: Two studies examined children's thought patterns in relation to their responses to social challenge. In Study 1, 4th and 5th graders tried out for a pen pal club under either a performance goal (stressing the evaluative nature of the tryout) or a learning goal (emphasizing the potential learning opportunities). In their behavior and attributions following rejection, children who were focused on a performance goal reacted with more helplessness, whereas children given a learning goal displayed a more mastery-oriented response. Study 2 found that in response to hypothetical socially challenging situations, 4th, 5th, and 6th graders who believed personality was nonmalleable (entity theorists) vs. malleable (incremental theorists) were more likely to endorse performance goals. Together, these studies indicate that children's goals in social situations are associated with their responses to social failure and are predicted by their implicit theories about their personality.

Social-contextual influences on expectancies for managing anger and sadness : The transition from middle childhood to adolescence

Abstract: This study examined the influence of emotion type (i.e., anger, sadness), audience type (i.e., mother, father, best friend), gender, and age on 140 5th-, 8th-, and 11th-grade adolescents' emotion management decisions, emotional self-efficacy, and outcome expectancies. Participants were read 8 vignettes and responded to 8 questions per vignette. Results indicated that 8th-grade adolescents reported regulating emotion most and expected the least interpersonal support from mothers. Children expressed greater self-efficacy and regulation of sadness than of anger. Boys reported dissembling emotion and expecting a negative interpersonal response to emotional behavior more than did girls. Children were more concerned with protecting feelings of friends than with protecting feelings of fathers.

Effect of skew, pole count and slot count on brushless motor radial force, cogging torque and back EMF

Abstract: Permanent magnet brushless motors are increasingly being used in high performance applications. In many of these applications, the acoustic noise and torque ripple characteristics of the motor are of primary concern. Because of this concern, it is important to understand the influence of the motor geometrical parameters of skew amount, pole count and slot count on the resulting motor characteristics of radial force, cogging torque and back EMF. While these relationships are understood intuitively and have been explored experimentally and predicted numerically, they have not been confirmed analytically for motors having any combination of skew amount, pole count and slot count. The paper fills this void by exploring these relationships analytically using a Fourier series. The influence of skew amount, pole count and slot count on motor radial force, cogging torque and back EMF are shown to confirm prior experimental and numerical results. More importantly, the derived analytical results provide valuable insight into the implications of common motor design choices.

Menopause-associated changes in plasma lipids, insulin-like growth factor I and blood pressure: a longitudinal study.

Abstract: We examined the effects of the menopause transition on plasma lipids, insulin-like growth factor I (IGF-I) and blood pressure. An initial cohort of 38, non-smoking, healthy premenopausal women (44-48 years) were examined at baseline and after a 6-year follow-up period. At follow-up, 18 women had spontaneously stopped menstruating, whereas 17 women remained premenopausal. Women who experienced natural menopause showed a greater decline in high-density lipoproteins (-5 +/- 4 mg dL-1 vs. -1 +/- 3 mg dL-1; P < 0.01) and a greater increase in low-density lipoproteins (13 +/- 12 vs. 5 +/- 10 mg dL-1; P < 0.05) and fasting triglycerides (14 +/- 15 vs. 5 +/- 11 mg dL-1; P < 0.05) than women who remained premenopausal. No menopause effect was noted for total cholesterol. We noted a greater decline in IGF-I levels in women who experienced a natural menopause (-21 +/- 11 ng mL-1) than women who remained postmenopausal (-4 +/- 10 ng mL-1). Systolic blood pressure increased in postmenopausal (13 +/- 10 mmHg) compared with premenopausal women (5 +/- 4 mmHg: P < 0.01), whereas no menopause effect was noted for diastolic blood pressure. The increase in the waist-to-hip ratio was related to a decrease in high-density lipoprotein (r = -0.49; P < 0.05) and increase in low-density lipoprotein (r = 0.48; P < 0.05). The decline in IGF-I was related to the decline in reported leisure time physical activity (0.44: P < 0.05). We conclude that the natural menopause transition is associated with a worsening of the lipid profile and decline in IGF-I, which might be mitigated by deleterious changes in body fat distribution and physical activity.

Responses of atmospheric methane consumption by soils to global climate change

Abstract: Soils consume about 40 Tg methane from the atmosphere annually. Thus, soils contribute significantly to the atmospheric methane budget. However, responses of atmospheric methane consumption to climate change are uncertain. Predicting these responses requires an understanding of the effect on methane consumption of specific variables (temperature and soil water content) as well as interactions among parameters (methane, ammonium, water content). Key considerations involve the limitations of diffusive transport and controls of methane diffusivity; limitation of methanotrophic activity by water stress; relatively slow growth rates of methane-oxidizing bacteria on atmospheric methane; ammonium toxicity. Interactions among these parameters may be particularly important, and lead to responses contrary to those predicted from changes in temperature and water content alone. Results from a number of analyses indicate that atmospheric methane consumption is especially sensitive to anthropogenic disturbances, which typically decrease activity. Continued increases in wet and dry ammonium deposition are likely to exacerbate inhibition resulting from changes in land use. Changes in hydrological regimes could further decrease activity if dry periods increase water stress at soil depths currently colonized by methanotrophs. Future trends in the soil methane sink are likely to lead to enhanced accumulation of atmospheric methane.

Variable expression of myoglobin among the hemoglobinless Antarctic icefishes

Abstract: The important intracellular oxygen-binding protein, myoglobin (Mb), is thought to be absent from oxidative muscle tissues of the family of hemoglobinless Antarctic icefishes, Channichthyidae Within this family of fishes, which is endemic to the Southern Ocean surrounding Antarctica, there exist 15 known species and 11 genera To date, we have examined eight species of icefish (representing seven genera) using immunoblot analyses Results indicate that Mb is present in heart ventricles from five of these species of icefish Mb is absent from heart auricle and oxidative skeletal muscle of all species We have identified a 09-kb mRNA in Mb-expressing species that hybridizes with a Mb cDNA probe from the closely related red-blooded Antarctic nototheniid fish, Notothenia coriiceps In confirmation that the 09-kb mRNA encodes Mb, we report the full-length Mb cDNA sequence of the ocellated icefish, Chionodraco rastrospinosus Of the eight icefish species examined, three lack Mb polypeptide in heart ventricle, although one of these expresses the Mb mRNA All species of icefish retain the Mb gene in their genomic DNA Based on phylogeny of the icefishes, loss of Mb expression has occurred independently at least three times and by at least two distinct molecular mechanisms during speciation of the family

Comparison of Hg and Pb fluxes to hummocks and hollows of ombrotrophic big heath bog and to nearby Sargent Mt. Pond, Maine, USA

Abstract: Two hummock cores (separated by I m), two hollow cores (separated by 1 m and both within 5 m of the hummock) from ombrotrophic Big Heath,and a single core from Sargent Mountain Pond (12 km north-northeast of the bog), Mt. Desert Island, Acadia National Park Maine, USA were collected in 1983 and dated using 210 Pb and analyzed for a suite of major and trace metals. The hummock cores correspond closely in terms of dating profiles, concentrations of Hg and Pb, and thus trends and values for accumulation rates. The hollow cores agree generally with each other but give more subdued peaks in concentration and lower integrated anthropogenic burdens of Hg and Pb and 50% lower unsupported 210 Pb than the hummock cores. Σ 210 Pb uns. (Bq/cm 2 ), ΣHg anth. (ng/cm 2 ), and ΣPb anth. (μg/cm 2 ) for the two hummock cores were 0.744 and 0.773, ≃ 130 and 130 (ng/cm 2 ), and ≃ 159 and 138 (μg/cm 2 ), respectively. The values for Sargent Mountain Pond were 0.411, 269, and 72, respectively. Hummock cores agree closely with the lake sediment core with respect to timing of maximum accumulation rates which occurred in the 1970s; Background atmospheric deposition rates of Hg and Pb to coastal Maine appear to have been about 2.5 to 3 ng/cm 2 /yr and <0.2 μg/cm 2 /yr, respectively. Atmospheric deposition of Hg and Pb increased to as much as 20 ng/cm 2 /yr and 2 μg/cm 2 /yr, respectively, by the 1970s and has decreased since then. Probably more than 50% of the Hg and Pb are deposited in dry and occult deposition.

Values of hypercompetitive and personal development competitive individuals.

Abstract: The value systems of hypercompetitive and personal development competitive individuals were examined in a sample of university undergraduates. As expected, people higher in hypercompetitiveness and in personal development competitiveness were both more likely to endorse values related to self-contained individualism such as achievement, hedonism, and a striving for an exciting and challenging life, but only hypercompetitives endorsed the value of power and control over others. Moreover, the data indicated that people higher in personal development competitiveness were more prone to endorse values related to ensembled individualism. In particular, they strongly endorsed values associated with social concern, that is, with caring about the well-being of others and with treating them with respect and as equals, whereas hypercompetitives expressed a lack of such concern. Discussion centered on the socialization process and how it can foster the development of different competitive orientations.

Role of age, education, and gender on cognitive performance in the Framingham Heart Study: community-based norms

Abstract: Normative data are presented for a neuropsychological test battery (Kaplan-Albert) consisting of subtests from the original Wechsler Adult Intelligence and Memory Scales and the Benton and Hamsher Aphasia Examination. Analyses were based on archival data resulting from administration (1976-1978) of the battery to community residents participating in the Framingham Heart Study, a prospective, longitudinal study of cardiovascular risk factors. Using 3 age groups (55-64, 65-74, and 75-88 years) and 4 education levels (5-8, 9-11, 12, > 12 years), individuals were stratified by age, gender, and education. Multiple linear regression analysis was used to relate main effects (age, education, and gender) and interactions of these effects to 9 test scores and to 2 composite scores identified by factor analysis. The oldest participants who had the fewest years of formal education had the lowest performance levels, with lower levels of performance for men than women in this least educated elderly cohort.

Modulation of Drosophila heartbeat by neurotransmitters

Abstract: The heart of Drosophila melanogaster is a simple muscular tube with a posterior pulsatile portion and a thoracic-cranial vessel. The pacemaker, located caudally, is myogenic. Its rate of firing is modulated by neurotransmitters. Serotonin, octopamine, norepineph-rine, dopamine, and acetylcholine accelerate the heart, in that order of potency. Dihydroxyphenylalanine, γ-aminobutyric acid, glutamate, and glycine have no effect. Generally, the regularity of the heartbeat is not adversely affected by treatment with any of these neurotransmitters. We show here that amnesiac, a neurological mutation, and Dihydroxyphenylalanine decarboxylase temperature sensitive, a mutation that interferes with synthesis of dopamine, norepinephrine, and serotonin, result in slower heart rate and reduced regularity across a normal range of temperatures for these flies. Dopamine-N-acetyltransferase, which is on the catabolic route to dopamine, serotonin, and octopamine, has no effect. hypoactiveC reduces the rate of the heart, but its mechanism of action is unknown.

Volumetric Properties of Carbon Dioxide + Acetone at High Pressures

Abstract: The volumetric properties of carbon dioxide + acetone mixtures have been determined at 323, 348, 373, 398, and 423 K at pressures up to 70 MPa using a variable-volume view cell. Densities for pure components and mixtures containing 90, 80, 70, and 50% by mass carbon dioxide are reported as a function of pressure at each temperature. It is shown that this system undergoes a density crossover at high pressures with each composition, a phenomenon previously reported also for mixtures of carbon dioxide + pentane and carbon dioxide + toluene. In the composition range investigated, the excess volume of the mixtures becomes more positive with increasing pressure but more negative with increasing temperature.

Qualitative Representation of Change

Abstract: Current geographic information systems (GISs) have been designed for querying and maintaining static databases representing static phenomena and give little support to those users who wish to represent dynamic information or incorporate temporality into their studies. In order to integrate phenomena that change over space and time in GISs, a better understanding of the underlying components of change and how people reason about change is needed. This paper focuses on a qualitative representation of change. It offers a classification of change based on object identity and the set of operations that either preserve or change identity. These operations can be applied to single or composite objects and combined to express the semantics of sequences of change. An iconic, visual language is developed to represent the various types of change and applied to examples to illustrate the application of this language. Such a formalization of the basic components of change lays the foundation for a new generation of formal models that captures the semantics of change and leads to improved interoperability between GISs and process models or simulation software.

Differences in tuber rot development for North American clones of Phytophthora infestans

Abstract: The relative aggressiveness ofPhytophthora infestons clones in potato tubers was compared in three trials using 7 to 24 isolates of 2 to 4 clones. Visible rot developed slowly at 13C with isolates of the US-1 genotype, the only significant clone found in North America prior to 1979, but substantially faster with most isolates of the newer clonal genotypes US-6, US-7 and US-8. Certain US-7 isolates were similar to US-1, and US-6 isolates also had a broad range of aggressiveness. Secondary infection byFusarium sp. increased rot development in many instances, but this effect was not clone-related. Differences in rot development may affect potato storage or late blight disease transmission.

Modeling hydrodynamics and aquaculture waste transport in coastal maine

Abstract: Net-pen aquaculture results in the introduction of excess fish food and fecal matter in coastal waters. These wastes may modify the benthic environment. Mathematical models are developed in this study to simulate tidal and wind-driven currents, waves, and the resulting dispersion of fish food and fecal matter in coastal Maine, a region where limited modelling studies have been performed. Cobscook Bay and Toothacher Bay in Maine are studied in detail through the use of mathematical models and field data. We find that a systematic, site-specific, step-by-step modeling strategy involving the use of numerical models to simulate the overall hydrodynamic environment in combination with a waste-particle transport model can be an extremely powerful method of determining a priori whether aquaculture operations will cause high rates of net-pen waste accumulation at a particular site.

Bacterial Endosymbionts in the Gills of the Deep-Sea Wood-Boring Bivalves Xylophaga atlantica and Xylophaga washingtona

Abstract: Bacterial endosymbionts found in gill tissues in several bivalve families convert otherwise unavailable energy sources (sulfide, methane, or cellulose) to forms readily metabolized by their hosts. We investigated the existence of such a symbiosis in two species of Xylophaga (family Pholadidae). The genus Xylophaga includes opportunistic species that are the predominant colonizers of wood at depths greater than 150 m. It has been hypothesized that, like their shallow-water counterparts the shipworms (family Teredinidae), species of Xylophaga utilize wood for nutrition. Results from transmission and scanning electron microscopy of X. atlantica and X. washingtona clearly demonstrate the presence of endosymbionts that resemble the shipworm endosymbionts both morphologically and in their anatomical location within the gills. Xylophaga and the teredinids both have a caecum packed with wood chips but lack the dense populations of microorganisms associated with cellulose digestion in termites or ruminants. These ...

Evolution of the mitochondrial DNA control region in the mbuna (Cichlidae) species flock of lake Malawi, East Africa

Abstract: Considerable controversy has surrounded the application of mitochondrial DNA data to reconstruction of evolutionary relationships among the endemic cichlids of Lake Malawi. Central to this debate has been the issue of whether lineage sorting is complete, and thus whether these data actually reflect species phylogeny, or simply gene genealogy. Review of all mtDNA control region sequences available for members of one monophyletic subset of this species flock, the Malawi rockfishes, or mbuna, strongly indicates that lineage sorting is incomplete: Character-based analyses of these sequences reconstruct gene, not species, interrelationships. Analysis of the pattern of nucleotide substitutions differentiating these mtDNA alleles suggests that pyrimidine residues undergo transition substitutions more often than do purines. Estimation of the magnitude of derived sequence differentiation in light of the reconstructed gene genealogy suggests that the mbuna may be of considerably more recent vintage than previous molecular characterizations have indicated.

Preventive Intervention as Means of Clarifying Direction of Effects in Socialization: Anxious-Withdrawn Preschoolers Case

Abstract: An indicated preventive intervention research program integrating attachment, attributional, and behaviorist perspectives was conducted to test the hypothesis that parent-child relationship disturbances directly effect the child's adjustment to the preschool. Anxious-withdrawn preschool children and their mothers were divided equally into treatment and control groups, and assessed on maternal self-report of parenting stress, behavioral ratings of mother-child interaction, and teacher ratings of the children in the preschool classroom. Results showed significant changes in the treatment of group: mothers in the treatment group moderated their level of control to a more appropriate, less intrusive level, while children in the treatment group showed an increase in cooperation and enthusiasm during a problem solving task with mother. Teacher-rated social competence and anxious-withdrawn behavior indicated improvement, although only the former was significant. The demonstration of effects of this home intervention for the mother on the child's behavior in the preschool confirm the transactional model underlying this study and demonstrate the utility of a parent-child interaction training component for the prevention of behavioral-emotional problems in young children.