University of Maine

About: University of Maine is a education organization based out in Orono, Maine, United States. It is known for research contribution in the topics: Population & Ice sheet. The organization has 8637 authors who have published 16932 publications receiving 590124 citations. The organization is also known as: University of Maine at Orono.

Burrowing mechanics: burrow extension by crack propagation.

Abstract: Until now, the analysis of burrowing mechanics has neglected the mechanical properties of impeding, muddy, cohesive sediments, which behave like elastic solids. Here we show that burrowers can progress through such sediments by using a mechanically efficient, previously unsuspected mechanism--crack propagation--in which an alternating 'anchor' system of burrowing serves as a wedge to extend the crack-shaped burrow. The force required to propagate cracks through sediment in this way is relatively small: we find that the force exerted by the annelid worm Nereis virens in making and moving into such a burrow amounts to less than one-tenth of the force it needs to use against rigid aquarium walls.

Oxygen production by endosymbiotic algae controls superoxide dismutase activity in their animal host

Abstract: Aerobic and aerotolerant organisms have evolved defenses against the toxic effects of molecular oxygen1. One protective mechanism involves the breakdown of the harmful superoxide radical by the enzyme superoxide dismutase (SOD). However, levels of oxygen elevated only slightly above normal atmospheric (P O2 of 159 mm Hg) may overpower a cell's defense systems2–4. Although most animals do not naturally encounter oxygen pressures above 1 atm, hyperbaric oxygen levels normally occur in the tissues of marine animals that harbour intracellular algal symbionts, which in light generate more oxygen than is consumed by the combined host and symbionts5–10. We have now found that sea anemones Anthopleura elegantissima (Brandt) containing zooxanthellae (the symbiotic dinoflagellate Symbiodinium microadriaticum) in their gastrodermal tissues have SOD activities nearly two orders of magnitude greater than individuals totally lacking zooxanthellae.

Regional insolation forcing of late Quaternary climate change in the Southern Hemisphere

Abstract: Southern New Zealand, positioned within the important southwesterly wind system, is a prime site for examining interhemispheric linkages in climate change. A series of cores drilled in the Okarito Pakihi peat bog now provides a continuous record of vegetation and climate change that may become a benchmark for the region. The data include clear evidence for modification of the global climate change signal in the Southern Hemisphere by local variation in the intensity of solar radiation. In agreement with the Milankovitch orbital forcing hypothesis1 it is often assumed that glacial–interglacial climate transitions occurred synchronously in the Northern and Southern hemispheres of the Earth. It is difficult to test this assumption, because of the paucity of long, continuous climate records from the Southern Hemisphere that have not been dated by tuning them to the presumed Northern Hemisphere signals2. Here we present an independently dated terrestrial pollen record from a peat bog on South Island, New Zealand, to investigate global and local factors in Southern Hemisphere climate changes during the last two glacial–interglacial cycles. Our record largely corroborates the Milankovitch model of orbital forcing but also exhibits some differences: in particular, an earlier onset and longer duration of the Last Glacial Maximum. Our results suggest that Southern Hemisphere insolation may have been responsible for these differences in timing. Our findings question the validity of applying orbital tuning to Southern Hemisphere records and suggest an alternative mechanism to the bipolar seesaw for generating interhemispheric asynchrony in climate change.

Online Mathematics Homework Increases Student Achievement

Abstract: In a randomized field trial with 2,850 seventh-grade mathematics students, we evaluated whether an educational technology intervention increased mathematics learning. Assigning homework is common y...

Biodiversity of micro-eukaryotes in Antarctic Dry Valley soils with <5% soil moisture

Abstract: Soils in the Dry Valleys of Antarctica are considered to be among the world's most extreme environments. These soils are old, cold and dry with low contents of organic carbon and nitrogen. Habitats adjacent to water (lakes and ice melts) have significant biological activity as demonstrated by the presence of algal mats, lichens and small invertebrates, particularly nematodes, tardigrades and rotifers. In contrast, there are extensive areas in the Dry Valleys that are extremely dry with less than 5% moisture content. These soils are often salty and appear to be barren of life as they have a coarse texture due to their lack of plant organic material. In contrast, molecular techniques (DNA extraction from soils, cloning and rDNA sequence analysis) demonstrated the presence of a complex micro-eukaryotic food web whose structure and composition varied with moisture content and location. Micro-eukaryotic communities in soils with 0.2-1.3% moisture were represented by species of the yeast genus Trichosporon and an unidentified clade of micro-eukaryotes, whereas levels from 3.1% to 4.9% contained complex food webs including primary producers (chlorophytes and stramenopiles), symbionts (lichen associated fungi), saprophytes (fungi), predators (alveolates and cercozoans) and fungal nematode parasite/pathogens. The soils had a diversity of species (80 species from 15 sites) with a restricted number (3-21 species) at each site. The sensitive and measurable community structure of the low moisture Dry Valley soils provides an unparalleled opportunity to examine local and global environmental effects on micro-eukaryotic community dynamics with multiple trophic levels.