209 research outputs found
The Minnesota Species of Aeshna with Notes on their Habits and Distribution (Odonata: Aeshnidae)
Apart from the well-known green darner, Anax junius, the species of Aeshna are the most familiar Minnesota Aeshnidae. These species are remarkably uniform in appearance. The basic body color is brown with blue, green, or yellow stripes on the thorax and with marks of similar color on the abdomen. Usually the spots of male specimens are blue, whereas green of various shades appears on most females. The individual species are not readily discernible to the novice collector
Intercalated Rare-Earth Metals under Graphene on SiC
Intercalation of rare earth metals ( = Eu, Dy, and Gd) is achieved by
depositing the metal on graphene that is grown on silicon-carbide (SiC)
and by subsequent annealing at high temperatures to promote intercalation. STM
images of the films reveal that the graphene layer is defect free and that each
of the intercalated metals has a distinct nucleation pattern. Intercalated Eu
forms nano-clusters that are situated on the vertices of a Moir{\`e} pattern,
while Dy and Gd form randomly distributed nano-clusters. X-ray magnetic
circular dichroism (XMCD) measurements of intercalated films reveal the
magnetic properties of these 's nano-clusters. Furthermore, field
dependence and temperature dependence of the magnetic moments extracted from
the XMCD show paramagnetic-like behaviors with moments that are generally
smaller than those predicted by the Brillouin function. XMCD measurements of
-oxides compared with those of the intercalated 's under graphene after
exposure to air for months indicate that the graphene membranes protect these
intercalants against oxidation.Comment: 9 pages, 7 figure
Intercalated europium metal in epitaxial graphene on SiC
X-ray magnetic circular dichroism (XMCD) reveal the magnetic properties of
intercalated europium metal under graphene on SiC(0001). Intercalation of Eu
nano-clusters (average size 2.5 nm) between graphene and SiC substate are
formed by deposition of Eu on epitaxially grown graphene that is subsequently
annealed at various temperatures while keeping the integrity of the graphene
layer. Using sum-rules analysis of the XMCD of Eu M edges at
K, our samples show paramagnetic-like behavior with distinct anomaly at T
90 K which may be related to the N{\`e}el transition, T = 91 K,
of bulk metal Eu. We find no evidence of ferromagnetism due to EuO or
antiferromagnetism due to EuO indicating that the graphene layer
protects the intercalated metallic Eu against oxidation over months of exposure
to atmospheric environment.Comment: 6 pages, 5 figure
Distribution and Habitat Preference of Minnesota Dragonfly Species (Odonata, Anisoptera) ll.
ABSTRACT - Five of the 70 Anisopteran species listed in this study represent new Minnesota recordings. Habitat zones are described and distribution of species within these zones are recorded by county of occurrence
Distribution and Habitat Preference of Minnesota Dragonfly Species (Odonata, Anisoptera) I.
The Anisoptera species found in Minnesota collections are listed. Eighteen of the 63 species are reported for the first time as occurring in Minnesota. The geographical distribution of the 63 species is presented. Factors affecting geographical distribution are discussed . The seasonal distribution of common species and genera with restricted flying times is discussed
Crystal Field and Dzyaloshinsky-Moriya Interaction in orbitally ordered La_{0.95}Sr_{0.05}MnO_3: An ESR Study
We present a comprehensive analysis of Dzyaloshinsky-Moriya interaction and
crystal-field parameters using the angular dependence of the paramagnetic
resonance shift and linewidth in single crystals of La_{0.95}Sr_{0.05}MnO_3
within the orthorhombic Jahn-Teller distorted phase. The Dzyaloshinsky-Moriya
interaction (~ 1K) results from the tilting of the MnO_6 octahedra against each
other. The crystal-field parameters D and E are found to be of comparable
magnitude (~ 1K) with D ~= -E. This indicates a strong mixing of the |3z^2-r^2>
and |x^2-y^2> states for the real orbital configuration.Comment: 12 pages, 6 figure
High Levels of Sediment Contamination Have Little Influence on Estuarine Beach Fish Communities
While contaminants are predicted to have measurable impacts on fish assemblages, studies have rarely assessed this potential in the context of natural variability in physico-chemical conditions within and between estuaries. We investigated links between the distribution of sediment contamination (metals and PAHs), physico-chemical variables (pH, salinity, temperature, turbidity) and beach fish assemblages in estuarine environments. Fish communities were sampled using a beach seine within the inner and outer zones of six estuaries that were either heavily modified or relatively unmodified by urbanization and industrial activity. All sampling was replicated over two years with two periods sampled each year. Shannon diversity, biomass and abundance were all significantly higher in the inner zone of estuaries while fish were larger on average in the outer zone. Strong differences in community composition were also detected between the inner and outer zones. Few differences were detected between fish assemblages in heavily modified versus relatively unmodified estuaries despite high concentrations of sediment contaminants in the inner zones of modified estuaries that exceeded recognized sediment quality guidelines. Trends in species distributions, community composition, abundance, Shannon diversity, and average fish weight were strongly correlated to physico-chemical variables and showed a weaker relationship to sediment metal contamination. Sediment PAH concentrations were not significantly related to the fish assemblage. These findings suggest that variation in some physico-chemical factors (salinity, temperature, pH) or variables that co-vary with these factors (e.g., wave activity or grain size) have a much greater influence on this fish assemblage than anthropogenic stressors such as contamination
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